Examine source code of Lichess Refined

{
  "manifest_version": 3,
  "name": "Lichess Refined",
  "version": "1.1",
  "description": "Modifies lichess.org homepage to add user info and remove clutter.",
  "icons": {
    "48": "lire48.png",
    "128": "lire128.png"
  },
  "action": {
    "default_popup": "index.html",
    "default_title": "Lichess Refined"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.lichess.org/"
      ],
      "css": [
        "lire.css"
      ],
      "js": [
        "lire.js",
        "loggedin.js"
      ]
    }
  ],
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "lire@rsazra.com"
    }
  }
}