Examine source code of jantama_cloth

{
  "manifest_version": 2,
  "name": "jantama_cloth",
  "version": "1.2",
  "description": "雀魂（じゃんたま）の背景を変更します",
  "permissions": [
    "storage",
    "webRequest",
    "webRequestBlocking",
    "https://game.mahjongsoul.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true,
    "open_in_tab": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{677d536b-f1ac-40dd-bbfb-898e9b9a4279}"
    }
  }
}