Add pre-commit hook for formatting

.pre-commit-config.yaml

@@ -0,0 +1,8 @@
+repos:
+-   repo: local
+    hooks:
+    -   id: prettier
+        name: prettier
+        language: system
+        entry: npx prettier --write
+        files: '\.tsx$'

default.nix

@@ -5,6 +5,7 @@ stdenv.mkDerivation {
     buildInputs = with pkgs; [
         create-react-app
         nodejs
+	pre-commit
 	yarn
     ];
     shellHook = ''