Add code of conduct

Author: hyperpolymath

CODE_OF_CONDUCT.md

@@ -0,0 +1,27 @@
+<!-- SPDX-License-Identifier: AGPL-3.0-or-later -->
+# Contributor Covenant Code of Conduct
+
+## Our Pledge
+
+We pledge to make participation a harassment-free experience for everyone.
+
+## Our Standards
+
+**Positive behavior:**
+* Using welcoming language
+* Being respectful of differing viewpoints
+* Accepting constructive criticism
+* Focusing on what is best for the community
+
+**Unacceptable behavior:**
+* Harassment, trolling, or personal attacks
+* Publishing private information without permission
+
+## Enforcement
+
+Report issues to the maintainers. All complaints will be reviewed.
+
+## Attribution
+
+Adapted from [Contributor Covenant](https://www.contributor-covenant.org/) v2.1.
+