feat: add treefmt to flake root

rust/default.nix

@@ -44,8 +44,9 @@
         # Build *just* the cargo dependencies, so we can reuse
         # all of that work (e.g. via cachix) when running in CI
         cargoArtifacts = craneLib.buildDepsOnly ({
-          inherit src buildInputs nativeBuildInputs;
-        } // cfg.cargoArtifacts.extraAttrs);
+            inherit src buildInputs nativeBuildInputs;
+          }
+          // cfg.cargoArtifacts.extraAttrs);
       in {
         options.krantz.rust = {
           enable = lib.mkEnableOption "building a cargo project with crane";
@@ -66,7 +67,11 @@
           srcToolchain = lib.mkOption {
             description = "A path to the rust-toolchain(.toml) file for the repo. Will use the toolchain from nixpkgs if the file does not exist.";
             type = lib.types.path;
-            default = "${if cfg.src != null then cfg.src else "/dev/null"}/rust-toolchain.toml";
+            default = "${
+              if cfg.src != null
+              then cfg.src
+              else "/dev/null"
+            }/rust-toolchain.toml";
             defaultText = lib.literalExpression "cfg.src + \"/rust-toolchain.toml\"";
             example = lib.literalExpression "./rust-toolchain";
           };
@@ -192,10 +197,10 @@
           # Your custom packages
           # Accessible through 'nix build', 'nix shell', 'nix run', etc
           packages = lib.mkIf cfg.package.enable {
-            ${cfg.package.name} =
-              craneLib.buildPackage ({
+            ${cfg.package.name} = craneLib.buildPackage ({
                 inherit src buildInputs nativeBuildInputs cargoArtifacts;
-              } // cfg.package.extraAttrs);
+              }
+              // cfg.package.extraAttrs);
           };
 
           # Formatter for nix files, available through 'nix fmt'