Newer AppImage process

[diegoiast]

I think that I am using the wrong tool to create an AppImage. If I remember, there are 2 tools, and I chosen the older one, which works but its not maintained.

How to make this PR:

• At start, fix build.sh (probably rename to build-appimage.sh. Fix it to use the new tool.
• Once its working - fix the github actions.
• Then rename build.bat into build-installer.bat.
• BONUS: build-macos-package.sh

RTFM:

• https://docs.appimage.org/packaging-guide/introduction.html
• https://stackoverflow.com/questions/71026584/packaging-qt-application-to-an-appimage-file-for-linux
• https://appimage-builder.readthedocs.io/en/latest/intro/tutorial.html