The app.desktop file shipped with the default build presumes the install
location of the binary. Let the OS determine the executable through it's
normal PATH variables.
Flatpak support has been a HUGE pain to keep working, the builds take
forever and cost me real money, and there are very few users. Ideally,
we want to just use native system packagers for each distro. I thought
Flatpak would make it easy to support many distros but that ended up
being false.
Inspired by #413.
This modifies the .desktop files so that it's possible to right-click on
the Ghostty icon in a dock and get the "New window" action.
Apparently this is how you implement that in GTK applications. In order
for us to also get "New tab", we'd have to implement a CLI flag, I
think.
