Add support for most secure install options

[Ganwtrs]

Verified Flatpak on Linux, App Store on macOS, and Microsoft Store on Windows

They each have sandboxing and app store verification

[max-privatevoid]

We could do Flathub, but if I were to make a Flatpak package, I'd like to package the thing such that it's actually sandboxed. The upstream logic is to immediately escape the sandbox via flatpak-spawn.