Add missing standard files

.github/CONTRIBUTING.md

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+First off, thanks for taking the time to contribute! ❤️
+
+All types of contributions are encouraged and valued.
+
+Before doing so, here are a few guidelines:
+
+* You agree to license your contributions under the project [license](LICENSE).
+* Use pull-requests early so it's open for discussion, even if your
+  contribution isn't ready yet.
+* All pull requests should include tests, as they help us avoid regressions in
+  our code.
+* A pull-request adding functionality should also update the documentation
+  accordingly.

.github/SECURITY.md

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+# Security Policy
+
+This code and its associated production web page are included in the Mozilla’s web and services [bug bounty program](https://www.mozilla.org/en-US/security/web-bug-bounty/). If you find a security vulnerability, please submit it via the process outlined in the program and [FAQ pages](https://www.mozilla.org/en-US/security/bug-bounty/faq-webapp/). Further technical details about this application are available from the [Bug Bounty Onramp page](https://wiki.mozilla.org/Security/BugBountyOnramp/).
+
+Please submit all security-related bugs through Bugzilla using the [web security bug form](https://bugzilla.mozilla.org/form.web.bounty). Never submit security-related bugs through a Github Issue or by email.

.github/SUPPORT.md

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+# Support
+
+See our [contact information](https://kitsune.readthedocs.io/en/latest/contactus.html#contact-us-chapter)!