Examine source code of かんたんコメントを薄くするやつ

{
  "manifest_version": 2,
  "name": "かんたんコメントを薄くするやつ",
  "version": "0.3.1",
  "browser_specific_settings": {
    "gecko": {
      "id": "comment-akkarin@rinsuki.net"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options.html"
  },
  "permissions": [
    "https://nmsg.nicovideo.jp/",
    "https://nvcomment.nicovideo.jp/",
    "https://www.nicovideo.jp/",
    "https://sp.nicovideo.jp/",
    "https://embed.nicovideo.jp/",
    "webRequestBlocking",
    "webRequest",
    "storage"
  ]
}