CONTRIBUTING.md: introduce a global contribution policy

CONTRIBUTING.md

@@ -0,0 +1,40 @@
+# Contributing to Void Linux
+
+This document is a guide for contributing to the Void Linux project. It applies
+to all repositories and community spaces, including GitHub, the Void Linux
+subreddit, and the Void Linux IRC channels.
+
+Additionally, some repositories may have their own `CONTRIBUTING.md` files.
+
+## General
+
+Contributions must have a clearly-defined authorship. If you are not submitting
+your own work (for example: patches from an upstream source or another
+distribution, content generated by a tool, or another person's work), it should
+be attributed to that work's author. Contributors must understand all changes
+they submit and be able to justify decisions made in their implementation.
+
+Examples of attribution include:
+
+- Git commit headers on patches
+- Links to changes in the originating version control system
+- a note in a commit message (`this change was generated using <tool>`)
+- a `Co-Authored-By:` trailer in a commit message
+
+## AI Usage
+
+*In this section, "AI" refers to generative artificial intelligence tools,
+including Large Language Models and similar technologies.*
+
+All contributions are expected to be made by humans. AI tools may be used for
+research and learning, but all content in contributions must originate from and
+be understood by the contributor. This includes code, documentation, issues,
+security reports, pull request descriptions, and comments in all Void Linux
+community spaces.
+
+ALL usage of AI tools MUST be disclosed.
+
+Do not bring AI review tools into pull requests.
+
+Usage of AI-powered human-language translation tools is acceptable to facilitate
+contributions across language barriers.