chore: add treefmt and format files

flake.nix

@@ -7,6 +7,7 @@
     flake-parts.lib.mkFlake {inherit inputs;} {
       imports = [
         inputs.devenv.flakeModule
+        inputs.treefmt-nix.flakeModule
         ./lib/flakeModule.nix
       ];
       systems = import systems;
@@ -14,16 +15,27 @@
       perSystem = {
         pkgs,
         inputs',
+        config,
         ...
       }: rec {
-        formatter = pkgs.alejandra;
+        treefmt = {
+          projectRootFile = "flake.nix";
+          programs = {
+            alejandra.enable = true;
+            mdformat.enable = true;
+            yamlfmt.enable = true;
+          };
+        };
         devenv.shells.default = {
           containers = pkgs.lib.mkForce {};
           packages = with pkgs; [dive skopeo];
 
           pre-commit = {
             hooks = {
-              alejandra.enable = true;
+              treefmt = {
+                enable = true;
+                packageOverrides.treefmt = config.treefmt.build.wrapper;
+              };
             };
           };
         };
@@ -157,6 +169,7 @@
       inputs.pre-commit-hooks.follows = "pre-commit-hooks";
     };
     pre-commit-hooks.url = "github:cachix/pre-commit-hooks.nix";
+    treefmt-nix.url = "github:numtide/treefmt-nix";
     attic = {
       url = "gitlab:TECHNOFAB/attic";
       inputs.nixpkgs.follows = "nixpkgs";