fix(windows): Show balloon when Keyman is already running

Fixes #4192.

If Keyman is already running, and the user attempts to start Keyman
again, a balloon will be shown to direct the user to the right place on
the screen.

Note: this worked in earlier versions of Keyman but stopped working due
to name changes for windows in the app.

I have also added a new string for balloon that will need translation.