Add StartupWMClass to .desktop file

resources/meta/com.github.iwalton3.jellyfin-media-player.desktop

@@ -6,6 +6,7 @@ Exec=jellyfinmediaplayer
 Icon=com.github.iwalton3.jellyfin-media-player
 Terminal=false
 Type=Application
+StartupWMClass=jellyfinmediaplayer
 Categories=AudioVideo;Video;Player;TV;
 
 Actions=DesktopF;DesktopW;TVF;TVW
@@ -24,4 +25,4 @@ Exec=jellyfinmediaplayer --fullscreen --tv
 
 [Desktop Action TVW]
 Name=TV [Windowed]
-Exec=jellyfinmediaplayer --windowed --tv
+Exec=jellyfinmediaplayer --windowed --tv