chore(nix): add pre-commit checks

flake.nix

@@ -5,6 +5,7 @@
     nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
     utils.url = "github:numtide/flake-utils";
     mkElmDerivation.url = "github:jeslie0/mkElmDerivation";
+    pre-commit-hooks.url = "github:cachix/pre-commit-hooks.nix";
   };
 
   outputs =
@@ -13,6 +14,7 @@
       nixpkgs,
       utils,
       mkElmDerivation,
+      pre-commit-hooks,
     }:
     utils.lib.eachDefaultSystem (
       system:
@@ -26,10 +28,13 @@
         devShells.default =
           with pkgs;
           mkShell {
-            buildInputs = [
+            inherit (self.checks.${system}.pre-commit-check) shellHook;
+
+            buildInputs = self.checks.${system}.pre-commit-check.enabledPackages ++ [
               elmPackages.elm
               elmPackages.elm-test
               elmPackages.elm-format
+              elmPackages.elm-review
               entr
             ];
           };
@@ -50,6 +55,18 @@
           };
         };
 
+        checks = {
+          pre-commit-check = pre-commit-hooks.lib.${system}.run {
+            src = ./.;
+            hooks = {
+              nixfmt-rfc-style.enable = true;
+              elm-format.enable = true;
+              # elm-review.enable = true;
+              # elm-test.enable = true;
+            };
+          };
+        };
+
         formatter = nixpkgs.legacyPackages.${system}.nixfmt-rfc-style;
       }
     );