Improve the metadata of the desktop file (#131)

* Fix desktop file mentioning cli wrapper

* Add more metadata to the desktop file

This makes it a bit easier to search for the application. You can for example search for "tailscale" or "vpn" now.

dev.deedles.Trayscale.desktop

@@ -3,8 +3,10 @@ Version=1.0
 Type=Application
 
 Name=Trayscale
-Comment=An unofficial GUI wrapper around the Tailscale CLI.
+GenericName=Tailscale Client
+Comment=An unofficial GUI interface for the Tailscale daemon.
 Categories=System;GNOME;GTK;
+Keywords=tailscale;vpn;
 
 Icon=dev.deedles.Trayscale
 Exec=trayscale