Adopt an AI policy

As of now contrib docs lack a section about AI usage:

Docs, testing and code should originate from your arguments/command lines usages/reflection. Commits messages and PR bodies should also be written/reviewed by you. Ideally linked to issues/discussions/docs.

Low-effort and large changes without proper scoping/testing, can be closed without explaining, and the same is true to issues.

Disclose usage/model in the PR/issues details and for what it was used (debugging, writing code, translating...).

I would say it should be tolerated, but with these 3 things I mind.

Refers to #4708