AppImage for Linux

[ghost]

AppImage for Linux could work across all Linux distributions.

Popular applications as Bitwarden and Joplin (Open Source alternative to EverNote) have begun to offer their app for Linux as an AppImage by default.

For integration with the system, "appimaged" can be installed by users and the instructions for it are very simple.

https://github.com/AppImage/AppImageKit#appimaged-usage

https://www.booleanworld.com/creating-linux-apps-run-anywhere-appimage/

[alichtman]

I'm happy to provide this option. This change will have to be made in package.json under the build key. I'll review a PR if you put it up. I've got too much on my plate at the moment to add this.