Coverpage: added link to discord server

Author: silseva

_coverpage.md

@@ -12,6 +12,7 @@ Top-down designed with modularity, flexibility and performance in mind.
 <a rel="me" href="https://mastodon.radio/@openrtx">Mastodon</a>
 [X](https://x.com/OpenRtx)
 [Matrix](https://matrix.to/#/#openrtx:matrix.org)
+[Discord](https://discord.com/invite/jZ9t8XTbmd)
 [Get Started](#the-openrtx-project)
 [Donate](https://liberapay.com/OpenRTX/donate)