Examine source code of niconico annict addon

{
  "name": "niconico-annict-addon",
  "author": "iamtakagi",
  "manifest_version": 2,
  "version": "1.0.2",
  "description": "ニコニコ動画で Annict の視聴記録管理を可能にする Firefox Addon",
  "permissions": [
    "https://www.nicovideo.jp/watch/*",
    "https://api.annict.com/*",
    "webRequest",
    "storage"
  ],
  "applications": {
    "gecko": {
      "id": "niconico-annict-addon@addons.iamtakagi.net"
    }
  },
  "options_ui": {
    "page": "settings.html"
  },
  "browser_action": {
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.nicovideo.jp/watch/*"
      ],
      "js": [
        "main.js"
      ]
    }
  ]
}