[Cin] AppImage for CinelerraGG testing

[Andrea paz]

I use Arch Linux KDE (Rolling always updated, now with kernel 5.10.13
and glibc 2.33)
I tested effects, transitions, Cuts with drag and drop, videoscopes,
OpenEDL, Nested clip and proxies. All OK for both "newer" and "older".
>From now on I will use only the newer.
Great job! Thanks MatN.

Stupid question: The sources size is 137MB, the AppImage is 79MB;
shouldn't the size of the AppImage be much larger?