Update 'gogs/LXC-RockyLinux.md'

Added reference for installing dark-theme from https://github.com/Kos-M/GogsThemes

gogs/LXC-RockyLinux.md

@@ -12,6 +12,7 @@ and will assumes that your server has:</summary>
 
 Out of scope:
 * reverse proxy in front of GOGS to make it available on default HTTP(s)port.<br>
+* Dark theme installation information on how to do that after setup : [https://github.com/Kos-M/GogsThemes](https://github.com/Kos-M/GogsThemes) <br>
 
 </details>
 </br>