add Code of Conduct

README.md

@@ -34,3 +34,7 @@ Did guidance related to an issue with Facebook or Apple bring you here? [Read th
 ## Email Communication Policy
 
 We tend to use the subject line tag "[PSL notification]" in all Public Suffix List communications. For effective spam filtering, you can create a case-insensitive filter to allow only emails with exact "[PSL notification]" in the subject line. If you choose to set up such a filter in your email application, please verify the filter is implemented correctly and test it thoroughly to ensure you don't accidentally miss important communications from us.
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+## Code of Conduct
+
+This project follows the [Mozilla Community Participation Guidelines](https://www.mozilla.org/en-US/about/governance/policies/participation/).