Linux Support, Packaging

[gomarcd]

Support for Linux began as a simple binary, which technically worked, people usually want something more than that.

Options being looked at include:

• AppImage
• A .deb or .rpm file
• Flatpak
• Snap

We should ideally provide good coverage without needing to maintain repositories for every distribution.

I have already added a working AppImage and .deb for now.

[gomarcd]

Flatpak and Snap have been added.

Will look at submission to Flathub and Snap Store, but need to tidy up a few items, fix missing icon in Snap installation and get submission requirements ready.

Edit: had to temporarily turn down Snap build as it was causing problems in the CI build. Will revisit.

[gomarcd]

Homebrew support was just added for Mac, going to see if it also works on Linux, I think it should.