create flatpak package

[qlrd]

Flatpak can be a universal package for all linux distros and can be run on separtate environment, protecting user.

See more on:

• https://www.electron.build/configuration/flatpak.html
• https://docs.flatpak.org/en/latest/electron.html

[Sami32]

I second that, thinking about using it in my TAILS OS.