Dear Maintainer,

Plz consider adding "--show" to the application desktop entry.

The current desktop entry launches Twinkle without the `--show` argument. This
causes inconsistent behavior when starting the application from a launcher or
dock. Without it, if Twinkle is already running and minimized/hidden to the
system tray, invoking the desktop entry again does not bring the existing
window back into focus. Instead an error message is displayed.

By changing the Exec line to call Twinkle with `--show`, both cases are handled
correctly:

1. If Twinkle is not running, `--show` starts it with the main window visible.
2. If Twinkle is already running (whether visible or hidden), `--show` will
raise/display the existing window.