Generate .flatpakref for all applications and addons

[razzeee]

We would like to make addons easily installable too, so having these created by flat-manager would be nice.

I think this area is one of the conditions, that needs change

flat-manager/src/jobs.rs

Line 456 in 7bfca06

let unwanted_exts = [".Debug", ".Locale", ".Sources", ".Docs"];

And maybe

flat-manager/src/jobs.rs

Line 629 in 7bfca06

if build_ref.ref_name.starts_with("app/") || build_ref.ref_name.starts_with("runtime/")