Provide packaging using CPack

This would allow for one-stop-shop configuring, building and packaging using CMake only.

for AppImage, see: https://github.com/AppImage/AppImageKit/issues/160#issuecomment-813069225
for macOS and Windows, CPack already supports them out of the box, albeit with some known issues.

This depends on #23 (closed), !122 (merged)

Also see !56

Edited Nov 15, 2021 by Dawid Wrobel