transition to MIT licence

[adrian-gierakowski]

AGPL is not compatible with nixpkgs, which makes contributions to this repo impossible to upstream.

Also, some of the code here (like comfyui module has been initially lifted from nixpkgs (which uses MIT licence).

Transition could be done as follows:

1. dual licence all code merged from now on (so that we only have to ask past contributors for re-licencing approval )
2. make a list of significant contributors (there are tools which help with that) and open an issue tagging everyone and asking for approval (I've seen this done on another nix project I contributed to)