temp/gnome-software: backport appstream from Alpine and add pmOS
While !1679 (closed) doesn't work because of a newer version of gnome-software that segfaults when you click a category, this backports Alpine's patch and adds postmarketOS' appstream.
This allows users to download through the store (even though many categories are empty) and it doesn't crash.
Tested on PP v1.2b
Edited by Administrator