Add a code of conduct and contributing file.

CONTRIBUTING.md

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+# Contributing
+
+Everyone is welcome to contribute to containers. Reach out to team members if you have questions:
+
+- IRC: #containers on irc.mozilla.org
+- Email: containers@mozilla.com
+
+## Filing bugs
+
+If you find a bug with containers, please file a issue.
+
+Check first if the bug might already exist: https://github.com/mozilla/testpilot-containers/issues
+
+[Open an issue](https://github.com/mozilla/testpilot-containers/issues/new)
+
+1. Visit about:support
+2. Click "Copy raw data to clipboard" and paste into the bug. Alternatively copy the following sections into the issue:
+  - Application Basics
+  - Nightly Features (if you are in nightly)
+  - Extensions
+  - Experimental Features
+3. Include clear steps to reproduce the issue you have experienced.
+4. Include screenshots if possible.
+
+## Sending Pull Requests
+
+Patches should be submitted as pull requests. When submitting patches as PRs:
+
+- You agree to license your code under the project's open source license (MPL 2.0).
+- Base your branch off the current master (see below for an example workflow).
+- Add both your code and new tests if relevant.
+- Run npm test to make sure all tests still pass.
+- Please do not include merge commits in pull requests; include only commits with the new relevant code.
+
+See the main [README](./README.md) for information on prerequisites, installing, running and testing.