Adding StartupWmClass for .desktop file

dist/org.yuzu_emu.yuzu.desktop

@@ -13,3 +13,4 @@ Exec=yuzu %f
 Categories=Game;Emulator;Qt;
 MimeType=application/x-nx-nro;application/x-nx-nso;application/x-nx-nsp;application/x-nx-xci;
 Keywords=Nintendo;Switch;
+StartupWMClass=yuzu