contributing: add link to IRC web chat
Contributing just involves sending a pull request. You will probably be more
successful with your contribution if you visit
-[#sway-devel on Libera.chat](https://libera.chat/guides/connect) upfront and
+[#sway-devel on Libera Chat](https://web.libera.chat/?channels=#sway-devel) upfront and
discuss your plans.
Note: rules are made to be broken. Adjust or ignore any/all of these as you see
