Update CONTRIBUTING.md with contacts and AI policy

- updated outdated links (used to be mailing lists, now pointing to our website's how to get in touch)
- include link to AI Policy for contributing (see also MDAnalysis/MDAnalysis.github.io#512 )

Author: orbeckst

.github/CONTRIBUTING.md

@@ -2,17 +2,17 @@
 
 Thanks for contributing to MDAnalysis!
 
-All members of the MDAnalysis community adhere to our [Code of Conduct](https://www.mdanalysis.org/pages/conduct/). By contributing code and interacting with us on GitHub, the forums, or by any other means you consent to follow the Code of Conduct.
+All members of the MDAnalysis community adhere to our [Code of Conduct](https://github.com/MDAnalysis/mdanalysis/?tab=coc-ov-file). By contributing code and interacting with us on GitHub, the forums, or by any other means you consent to follow the Code of Conduct.
 
 #### Reporting issues
 
 If you've found a defect with MDAnalysis we'd love to know so we can fix it.  Please follow the Issue template so we can quickly diagnose the problem, in particular the piece of code that causes the problem.
 
-If your issue isn't a defect with the code and instead you require help using MDAnalysis, drop by the [discussion forum](https://groups.google.com/forum/#!forum/mdnalysis-discussion).
+If your issue isn't a defect with the code and instead you require help using MDAnalysis, drop by in [discord #users or GitHub discussions](https://www.mdanalysis.org/community/#ask-questions--get-help).
 
 #### Contributing code
 
-If you're contributing code, please check out [How to contribute](https://www.mdanalysis.org/UserGuide/contributing.html) in the User Guide and look at the [Style guide](https://github.com/MDAnalysis/mdanalysis/wiki/Style-Guide).
+We welcome your code contributions! Please check out the [Contributing](https://www.mdanalysis.org/contribute/) section on our web page for how you can contribute to the whole MDAnalysis project and in particular the [User Guide's section on Contributing](https://userguide.mdanalysis.org/stable/contributing_code.html) for the MDAnalysis package in particular. Please also familiarize yourself with the current version of our [AI Policy](https://github.com/MDAnalysis/mdanalysis/blob/develop/AI_POLICY.md)
 
-MDAnalysis devs are most easily reached through the [development list](https://groups.google.com/forum/#!forum/mdnalysis-devel).
+MDAnalysis devs are most easily reached in the [discord #developers channel](https://www.mdanalysis.org/community/#ask-questions--get-help).