feat: nix flake

[not-a-cowfr]

adds
- devshell
- swiftly package
- paicord package (soon)

im not a swift person so i dont really know the swift process but i believe after entering the flake with swiftly you have to do

swiftly init # it gave me an error that nixos isnt supported but i just picked ubuntu 24 and it seemed to work
swiftly install --use latest

and then after that you should be good for whatever devshells you enter

i also cant test on anything besides x86_64-linux but im pretty sure ive correctly added support for macos and other architectures

[blahai]

swift is a fuck and this is so insanely impure that until swift 6 is in nixpkgs there can't really be a package for paicord, devshell is the best we can do until then

also this flake kinda ass I'm making a better one once (if) I can figure out the gcc issues

[blahai]

actually a paicord package could be possible if we get ci to build a static linux bin but that also seems like a pita so maybe as a last resort