AI/LLM contribution policy

Nobody has claimed this yet.

I've noticed in the past few months several open source projects have had debates about dealing with LLM-assisted contributions, with widely diverging decisions; e.g. QEMU [bans](https://github.com/qemu/qemu/commit/3d40db0efc22520fa6c399cf73960dced423b048) it outright, out of concern for future legal issues with copyright, while others like [Fedora](https://docs.fedoraproject.org/en-US/council/policy/ai-contribution-policy/) and [LLVM](https://discourse.llvm.org/t/rfc-llvm-ai-tool-policy-start-small-no-slop/88476) regulate it.

I think it's fair to say that there's already some LLM-contributed code merged in M2, but presumably it won't be long before we have to review package pull requests with LLM written documentation. I think it would be good to establish some ground rules ahead of time and advertise it in our [pull request template](https://github.com/Macaulay2/M2/blob/stable/.github/pull_request_template.md?plain=1).

Start by reviewing the existing .github/pull_request_template.md and the linked QEMU, Fedora, and LLVM policies. The issue does not specify which rules M2 should adopt, so the work first needs an agreed policy; done would mean documenting that policy and reflecting it in the pull request template.

Written by the indexing model from the issue text.