add StartupWMClass in desktop file

makes gnome associate the window with the desktop file so the icon can be show in the taskbar

Author: LiAlH4qwq

en/guide/01-install.md

@@ -56,13 +56,13 @@ Create the desktop shortcut manually: create a file named `GUI.for.Clash.desktop
 Version=1.0
 Name=GUI.for.Clash
 Comment=GUI.for.Clash
+StartupWMClass=GUI.for.Clash
 Exec=/path/to/GUI.for.Clash/GUI.for.Clash
 Icon=/path/to/GUI.for.Clash/appicon.png
 Terminal=false
 Type=Application
 Categories=Application;GUI.for.Clash;
 StartupNotify=true
-
 ```
 
 ## 5. Directory Dissection