community: Add Matrix link

Forwarded: https://booting.oniroproject.org/distro/docs/-/merge_requests/230
Bug: https://git.ostc-eu.org/distro/docs/-/issues/86
Relate-to: https://git.ostc-eu.org/distro/docs/-/merge_requests/211


Signed-off-by: Philippe Coval <philippe.coval@huawei.com>

community-chat-platform.rst

@@ -33,3 +33,6 @@ The user might prefer to install an IRC client to connect to #oniroproject chann
 
   
 More details are explained on `the Libera website <https://libera.chat/guides/connect>`_.
+
+Another possibility to use this IRC room is to use our `Matrix bridge to IRC <https://matrix.to/#/#oniroproject:libera.chat>`_.
+One benefit is that everyone can catch up by reading existing logs on reconnection.