- use the same approach as status-go to detect the image type, relying
on "magic" type matching instead of looking at the file extension (now
using C++ and QMime*)
- add a little error popup when the user tries to upload an unsupported
image type while creating/editing a community
- expose all the image related properties from the C++ backend instead
of constructing and duplicating them in QML
- cleanup some unused/dead code
Fixes#16668
623333ab8c