Add Type=Application in bin/plasma-mobile.desktop to have plasma-mobile recognized by phog

Hi and thank you for developing Plasma mobile!

Mobian distribution has been including phog greeter by default for some time now, but when plasma-mobile gets installed (for now, using a separate deb file I built), phog does not recognize it.

By comparing /usr/share/wayland-sessions/plasma-mobile.desktop with the phosh one, I found out the problem is the missing Type=Application line.

After manually changing the desktop file, PM session gets correctly listed:

I have also reported this to phog, but I am not able to understand if a fix is feasible inside phog. Considering unknown if/when phog will be fixed, I do not think one added line in the PM desktop file will do any harm 😄