Should provide /usr/share/applications/sm.puri.OSK0.desktop via /etc/alternatives/Phosh-OSK

I'd be good if squeekboard would handle sm.puri.OSK0 via update-alternatives like librem5-base and phosh-osk-stub do.

Otherwise there's no OSK for phosh's session which doesn't end well (with a black screen in byzantium (not nice) with a fail whale in crimson (correct way), see See Librem5/OS-issues#319 (comment 236833) .

The easiest fix would be to base this package on Debian's squeekboard packaging which handles this since 1.20.0-2 (Nov 22).