Format src files with Prettier (#215)

Formats files in `src` with [prettier for consistent code style](https://prettier.io/docs/en/why-prettier) and adds npm script

Related to https://github.com/webrecorder/replayweb.page/issues/201

package.json

@@ -34,9 +34,11 @@
     "electron-builder": "^23.0.3",
     "electron-notarize": "^1.1.1",
     "eslint": "^8.23.1",
+    "eslint-config-prettier": "^9.0.0",
     "http-server": "^13.0.2",
     "mini-css-extract-plugin": "^2.3.0",
     "node-sass": "^9.0.0",
+    "prettier": "^3.0.1",
     "raw-loader": "^4.0.2",
     "sass-loader": "^13.3.2",
     "style-loader": "^3.2.1",
@@ -67,7 +69,8 @@
     "dist": "yarn run build && yarn run pack",
     "dist-dev": "yarn run build-dev && yarn run pack",
     "release": "yarn run build && electron-builder",
-    "lint": "eslint ./src/ webpack.config.js"
+    "lint": "eslint ./src/ webpack.config.js",
+    "format": "prettier --write ./src"
   },
   "build": {
     "afterSign": "build/notarize.js",