Add prettier.

package.json

@@ -4,7 +4,8 @@
   "description": "",
   "main": "index.jsx",
   "scripts": {
-    "dev": "webpack server"
+    "dev": "webpack server",
+    "format": "prettier --write '**/*.{json,js,ts,tsx,css}'"
   },
   "keywords": [],
   "author": "",
@@ -23,6 +24,7 @@
     "css-loader": "^6.9.1",
     "html-webpack-plugin": "^5.6.0",
     "postcss-loader": "^8.0.0",
+    "prettier": "^3.2.4",
     "style-loader": "^3.3.4",
     "ts-loader": "^9.5.1",
     "typescript": "^5.3.3",