provides:
- nix develop: dev shell with nodejs, qrencode, imagemagick
- nix run .#qr: generate qr codes from urls
- nix run .#qr-slides: generate qr for course urls
- nix run .#optimize-img: resize images to max width
- dev servers on ports 1311 (index), 1312, 1313
- build/deploy targets for both courses
- qr code generation via nix-shell
- image optimization support