Update CONTRIBUTING with instructions for sending patches

CONTRIBUTING.md

@@ -65,8 +65,9 @@ It is frequently asked by would-be contributors whether I have tips for an
 optimal ramping up of skills. [I've put together a little document to answer
 that question](https://collapseos.org/skills.html).
 
-## No typo pull requests please
+## Sending patches
 
-Please, don't open pull requests to fix typos. See [issue #3][GH-3] for details.
+If you have patches to submit, please do so through the [mailing list][ml]. See
+<https://git-send-email.io/> for a guide.
 
-[GH-3]: https://github.com/hsoft/collapseos/pull/3
+[ml]: https://lists.sr.ht/~vdupras/collapseos