Add changelog, code of conduct, contributing

Added changelog, code of conduct, contributing.

CHANGELOG.md

+# Changelog
+All notable changes to this project will be documented in this file.
+
+## [Unreleased]

CODE_OF_CONDUCT.md

+
+# Contributor Covenant Code of Conduct
+
+## Our Pledge
+
+We as members, contributors, and leaders pledge to make participation in our community a harassment-free experience for everyone, regardless of age, body size, visible or invisible disability, ethnicity, sex characteristics, gender identity and expression, level of experience, education, socio-economic status, nationality, personal appearance, race, religion, or sexual identity and orientation.
+
+We pledge to act and interact in ways that contribute to an open, welcoming, diverse, inclusive, and healthy community.
+
+## Our Standards
+
+Examples of behavior that contributes to a positive environment for our community include:
+
+* Demonstrating empathy and kindness toward other people
+* Being respectful of differing opinions, viewpoints, and experiences
+* Giving and gracefully accepting constructive feedback
+* Accepting responsibility and apologizing to those affected by our mistakes, and learning from the experience
+* Focusing on what is best not just for us as individuals, but for the overall community
+
+Examples of unacceptable behavior include:
+
+* The use of sexualized language or imagery, and sexual attention or
+  advances of any kind
+* Trolling, insulting or derogatory comments, and personal or political attacks
+* Public or private harassment
+* Publishing others' private information, such as a physical or email
+  address, without their explicit permission
+* Other conduct which could reasonably be considered inappropriate in a
+  professional setting
+
+## Enforcement Responsibilities
+
+Community leaders are responsible for clarifying and enforcing our standards of acceptable behavior and will take appropriate and fair corrective action in response to any behavior that they deem inappropriate, threatening, offensive, or harmful.
+
+Community leaders have the right and responsibility to remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned to this Code of Conduct, and will communicate reasons for moderation decisions when appropriate.
+
+## Scope
+
+This Code of Conduct applies within all community spaces, and also applies when an individual is officially representing the community in public spaces. Examples of representing our community include using an official e-mail address, posting via an official social media account, or acting as an appointed representative at an online or offline event.
+
+## Enforcement
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be reported to the community leaders responsible for enforcement at hello@jenssegers.com. All complaints will be reviewed and investigated promptly and fairly.
+
+All community leaders are obligated to respect the privacy and security of the reporter of any incident.
+
+## Enforcement Guidelines
+
+Community leaders will follow these Community Impact Guidelines in determining the consequences for any action they deem in violation of this Code of Conduct:
+
+### 1. Correction
+
+**Community Impact**: Use of inappropriate language or other behavior deemed unprofessional or unwelcome in the community.
+
+**Consequence**: A private, written warning from community leaders, providing clarity around the nature of the violation and an explanation of why the behavior was inappropriate. A public apology may be requested.
+
+### 2. Warning
+
+**Community Impact**: A violation through a single incident or series of actions.
+
+**Consequence**: A warning with consequences for continued behavior. No interaction with the people involved, including unsolicited interaction with those enforcing the Code of Conduct, for a specified period of time. This includes avoiding interactions in community spaces as well as external channels like social media. Violating these terms may lead to a temporary or permanent ban.
+
+### 3. Temporary Ban
+
+**Community Impact**: A serious violation of community standards, including sustained inappropriate behavior.
+
+**Consequence**: A temporary ban from any sort of interaction or public communication with the community for a specified period of time. No public or private interaction with the people involved, including unsolicited interaction with those enforcing the Code of Conduct, is allowed during this period. Violating these terms may lead to a permanent ban.
+
+### 4. Permanent Ban
+
+**Community Impact**: Demonstrating a pattern of violation of community standards, including sustained inappropriate behavior,  harassment of an individual, or aggression toward or disparagement of classes of individuals.
+
+**Consequence**: A permanent ban from any sort of public interaction within the community.
+
+## Attribution
+
+This Code of Conduct is adapted from the [Contributor Covenant][homepage], version 2.0,
+available at https://www.contributor-covenant.org/version/2/0/code_of_conduct.html.
+
+Community Impact Guidelines were inspired by [Mozilla's code of conduct enforcement ladder](https://github.com/mozilla/diversity).
+
+[homepage]: https://www.contributor-covenant.org
+
+For answers to common questions about this code of conduct, see the FAQ at
+https://www.contributor-covenant.org/faq. Translations are available at https://www.contributor-covenant.org/translations.

CONTRIBUTING.md

+# Contributing
+
+Contributions are **welcome** and will be fully **credited**.
+
+Please read and understand the contribution guide before creating an issue or pull request.
+
+## Etiquette
+
+This project is open source, and as such, the maintainers give their free time to build and maintain the source code
+held within. They make the code freely available in the hope that it will be of use to other developers. It would be
+extremely unfair for them to suffer abuse or anger for their hard work.
+
+Please be considerate towards maintainers when raising issues or presenting pull requests. Let's show the
+world that developers are civilized and selfless people.
+
+It's the duty of the maintainer to ensure that all submissions to the project are of sufficient
+quality to benefit the project. Many developers have different skillsets, strengths, and weaknesses. Respect the maintainer's decision, and do not be upset or abusive if your submission is not used.
+
+## Viability
+
+When requesting or submitting new features, first consider whether it might be useful to others. Open
+source projects are used by many developers, who may have entirely different needs to your own. Think about
+whether or not your feature is likely to be used by other users of the project.
+
+## Procedure
+
+Before filing an issue:
+
+- Attempt to replicate the problem, to ensure that it wasn't a coincidental incident.
+- Check to make sure your feature suggestion isn't already present within the project.
+- Check the pull requests tab to ensure that the bug doesn't have a fix in progress.
+- Check the pull requests tab to ensure that the feature isn't already in progress.
+
+Before submitting a pull request:
+
+- Check the codebase to ensure that your feature doesn't already exist.
+- Check the pull requests to ensure that another person hasn't already submitted the feature or fix.
+
+## Requirements
+
+If the project maintainer has any additional requirements, you will find them listed here.
+
+- **[PSR-2 Coding Standard](https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md)** - The easiest way to apply the conventions is to install [PHP Code Sniffer](https://pear.php.net/package/PHP_CodeSniffer).
+
+- **Add tests!** - Your patch won't be accepted if it doesn't have tests.
+
+- **Document any change in behaviour** - Make sure the `README.md` and any other relevant documentation are kept up-to-date.
+
+- **Consider our release cycle** - We try to follow [SemVer v2.0.0](https://semver.org/). Randomly breaking public APIs is not an option.
+
+- **One pull request per feature** - If you want to do more than one thing, send multiple pull requests.
+
+- **Send coherent history** - Make sure each individual commit in your pull request is meaningful. If you had to make multiple intermediate commits while developing, please [squash them](https://www.git-scm.com/book/en/v2/Git-Tools-Rewriting-History#Changing-Multiple-Commit-Messages) before submitting.
+
+**Happy coding**!