docs(open source): add contributing and code of conduct docs (#326)

* docs(open source): add contributing and code of conduct docs

* Update CONTRIBUTING.md

Co-authored-by: Daniel Brooks <[email protected]>

Co-authored-by: Daniel Brooks <[email protected]>

Author: jpetto

CODE_OF_CONDUCT.md

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+# Community Participation Guidelines
+
+This repository is governed by Mozilla's code of conduct and etiquette guidelines.
+For more details, please read the
+[Mozilla Community Participation Guidelines](https://www.mozilla.org/about/governance/policies/participation/).
+
+## How to Report
+
+For more information on how to report violations of the Community Participation Guidelines, please read our '[How to Report](https://www.mozilla.org/about/governance/policies/participation/reporting/)' page.

CONTRIBUTING.md

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+## Contributing
+
+Thank you for checking out our Collection API work. We welcome contributions from everyone! By participating in this project, you agree to abide by the Mozilla [Community Participation Guidelines](https://www.mozilla.org/about/governance/policies/participation/).
+
+### Asking questions / receiving updates
+
+- Slack channel (Pocket staff only): #p-curation-tools
+
+- File issues/questions on Github: [https://github.com/Pocket/collection-api/issues](https://github.com/Pocket/collection-api/issues). We typically triage new issues every Monday.
+
+### Finding Bugs & Filing Tickets
+
+If you've found a bug, or have a feature idea that you you'd like to see, follow these simple guidelines:
+
+- Pick a thoughtful and concise title for the issue (ie. _not_ Thing Doesn't Work!)
+
+- Make sure to mention your local configuration, OS and basic system parameters
+
+- If you can reproduce the bug, give a step-by-step recipe
+
+- Include stack traces from the console(s) where appropriate
+
+- Screenshots and screen recordings welcome!
+
+- When in doubt, take a look at some existing issues and emulate
+
+### Contributing Code
+
+If you are new to the repo, you might want to pay close attention to these tags, as they are typically a great way to get started: Good First Bug, Bug, Chore, and Polish. If you see a bug that is not yet assigned to anyone, start a conversation with an engineer in the ticket itself, expressing your interest in taking the bug. If you take the bug, someone will set the ticket to Assigned to Contributor, so we can be proactive about helping you succeed in fixing the bug.
+
+When you have some code written, you can open up a Pull Request, get your code reviewed, and see your code merged into the codebase.
+
+### Setting up your development environment
+
+Please review the [README](https://github.com/Pocket/collection-api/blob/main/README.md) for instructions on setting up your development environment, installing dependencies and building the extensions.
+
+### Creating Pull Requests
+
+You have identified the bug, written code and now want to get it into the main repo using a [Pull Request](https://help.github.com/articles/about-pull-requests/).
+
+All code is added using a pull request against the master branch of our repo. Before submitting a PR, please go through this checklist:
+
+- All tests must pass (and if you haven't written a test, please do!)
+
+- Fill out the pull request template as outlined
+
+- Please add a PR / Needs Review tag to your PR (if you have permission). This starts the code review process. If you cannot add a tag, don't worry, we will add it during triage.
+
+- Make sure your PR will merge gracefully with master at the time you create the PR, and that your commit history is 'clean'
+
+### Understanding Code Reviews
+
+You have created a PR and submitted it to the repo, and now are waiting patiently for you code review feedback. One of the projects module owners will be along and will either:
+
+- Make suggestions for some improvements
+
+- Give you a 👍 in the comments section, indicating the review is done and the code can be merged
+
+Typically, you will iterate on the PR, making changes and pushing your changes to new commits on the PR. When the reviewer is satisfied that your code is good-to-go, you will get the coveted R+ comment, and your code can be merged. If you have commit permission, you can go ahead and merge the code to master, otherwise, it will be done for you.
+
+Our project prides itself on its respectful, patient and positive attitude when it comes to reviewing contributors' code, and as such, we expect contributors to be respectful, patient and positive in their communications as well.
+
+### Commit format
+
+Commits should be formated as `type(scope): message`
+
+The following types are allowed:
+
+| Type     | Description                                                                                           |
+| -------- | ----------------------------------------------------------------------------------------------------- |
+| feat     | A new feature                                                                                         |
+| fix      | A bug fix                                                                                             |
+| docs     | Documentation only changes                                                                            |
+| style    | Changes that do not affect the meaning of the code (white-space, formatting,missing semi-colons, etc) |
+| refactor | A code change that neither fixes a bug nor adds a feature                                             |
+| perf     | A code change that improves performance                                                               |
+| test     | Adding missing or correcting existing tests                                                           |
+| chore    | Changes to the build process or auxiliary tools and libraries such as documentation generation        |
+
+### Writing Good Git Commit Messages
+
+We use standard changelog and enforce [conventional commits](https://www.conventionalcommits.org/).
+
+We like this overview by Chris Beams on "[How to Write a Git Commit Message](https://chris.beams.io/posts/git-commit/)".
+
+The tl;dr is:
+
+1. [Separate subject from body with a blank line](https://chris.beams.io/posts/git-commit/#separate)
+
+2. [Limit the subject line to 50 characters](https://chris.beams.io/posts/git-commit/#limit-50)
+
+3. [Capitalize the subject line](https://chris.beams.io/posts/git-commit/#capitalize)
+
+4. [Do not end the subject line with a period](https://chris.beams.io/posts/git-commit/#end)
+
+5. [Use a verb to start your subject line (Add, Remove, Fix, Update, Rework, Polish, etc.)](https://chris.beams.io/posts/git-commit/#imperative)
+
+6. [Wrap the body at 72 characters](https://chris.beams.io/posts/git-commit/#wrap-72)
+
+7. [Use the body to explain _what_ and _why_ vs. _how_](https://chris.beams.io/posts/git-commit/#why-not-how)
+
+### Understanding How Pocket Triages
+
+The project team meets weekly (in a closed meeting, for the time being), to discuss project priorities, to triage new tickets, and to redistribute the work amongst team members. Any contributors tickets or PRs are carefully considered, prioritized, and if needed, assigned a reviewer.