feat(nix): add `nixfmt-classic`

Signed-off-by: Seongmin Lee <git@boltless.me>

boltless.me cef3dbdf 546fc335

verified
Changed files
+1
nix
+1
nix/flake.nix
··· 78 78 pkgs.meld 79 79 pkgs.mprocs 80 80 pkgs.nil 81 + pkgs.nixfmt-classic 81 82 pkgs.nodejs_24 82 83 pkgs.pandoc 83 84 pkgs.qmk