fix: Enable Loop mode sync for MPRIS

Loop mode changes were being correctly reflected in Supersonic, when
updated in the toolbar, but not the other way around. We were only
missing an `Options` changes emit when loop mode is changed in
Supersonic.

backend/mpris.go

@@ -73,6 +73,11 @@ func NewMPRISHandler(playerName string, pm *PlaybackManager) *MPRISHandler {
 			m.evt.Player.OnVolume()
 		}
 	})
+	pm.OnLoopModeChange(func(loopMode LoopMode) {
+		if m.connErr == nil {
+			m.evt.Player.OnOptions()
+		}
+	})
 	emitPlayStatus := func() {
 		if m.connErr == nil {
 			m.evt.Player.OnPlayPause()