Examine source code of Chess.com RU/BY flags

{
  "manifest_version": 2,
  "name": "Chess.com RU/BY flags",
  "version": "1.1",
  "description": "Replaces gray flags on chess.com with RU or BY flag.",
  "icons": {
    "128": "icons/icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.chess.com/*"
      ],
      "js": [
        "chessFlags.js"
      ]
    }
  ],
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ab7a0282-fb5d-4cb2-b65a-fdda2b8e8cea}"
    }
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "128": "icons/icon128.png"
    }
  }
}