Provide up to date docker image/ appimage

[KelvinChung2000]

We now have nix, but in some lockdown-controlled systems, they might only be equipped with Docker or maybe nothing.

A guide to export docker image from Nix:
https://nix.dev/tutorials/nixos/building-and-running-docker-images.html

A guide to export appimage from Nix:
https://github.com/ralismark/nix-appimage

[KelvinChung2000]

And even maybe VM image and do this once and for all

https://github.com/nix-community/nixos-generators