Sozi release 22.02.20 for testers

This intermediate release aims at fixing installation issues and testing new packaging options.
It addresses the following concerns:

• Debian packages should be installable in Debian, Ubuntu and their derivatives (#572)
• RPM packages should not conflict with other Electron applications (#605)
• Linux users will now benefit from an AppImage package (#602)
• Windows users will be able to install Sozi using an executable installer.

If you want to help me improve Sozi, please try to install one or more of these packages and report any success or issue that you encounter.