Package: add TryExec to desktop file (#204)

Package/com.github.Rosalie241.RMG.desktop

@@ -3,6 +3,7 @@ Type=Application
 Name=Rosalie's Mupen GUI
 Comment=An easy to use & cross-platform mupen64plus front-end written in C++ & Qt
 Exec=RMG %f
+TryExec=RMG
 Icon=com.github.Rosalie241.RMG
 Terminal=false
 Categories=Game;Emulator;Qt;