Add snap package

[jhoermann]

Would be great to have a Linux snap package for easier installs. There are also other options like flatpak or appimage but as Ubuntu is the most used Linux distribution I think snap would be a good starting point.

[fmaclen]

If anyone wants to contribute to this feature take a look at the config in:

• electron-builder.yml
• .github/workflows/release.yml

[savchenko]

There are many, many issues with snaps and AFAIK Ubuntu is the only distribution using them. Appimage would run virtually anywhere as the single binary. Flatpak has its advantages, but requires flatpak framework installed.