add info about ai pull requests

Author: Boy132

CONTRIBUTING.md

@@ -24,6 +24,9 @@ If you add a new plugin, make sure to update the main README.
 
 Also, please make sure that your pull requests are as targeted and simple as possible and don't do a hundred things at a time. If you want to add/change/fix 5 different things you should make 5 different pull requests.
 
+>[!IMPORTANT]
+> Pull requests that are entirely (or mostly) generated by AI will not be accepted. If you use AI for some parts you have to clearly indicate that in the PR description.
+
 ## Community and Support
 
 * Help: [Discord](https://discord.gg/pelican-panel)