Examine source code of Radon

{
  "manifest_version": 2,
  "name": "Radon",
  "version": "2.3.1.429",
  "description": "Track and share your listening and watching activity with Last.fm, Libre.fm, ListenBrainz and Trakt.tv",
  "applications": {
    "gecko": {
      "id": "jid1-rbAJu4BHjMqTww@jetpack",
      "strict_min_version": "59.0a1"
    }
  },
  "icons": {
    "16": "Resources/Icons/application/16.png",
    "24": "Resources/Icons/application/24.png",
    "32": "Resources/Icons/application/32.png",
    "48": "Resources/Icons/application/48.png",
    "64": "Resources/Icons/application/64.png",
    "96": "Resources/Icons/application/96.png",
    "128": "Resources/Icons/application/128.png"
  },
  "permissions": [
    "*://play.google.com/music/*",
    "*://ws.audioscrobbler.com/2.0/*",
    "storage",
    "tabs",
    "unlimitedStorage"
  ],
  "optional_permissions": [
    "*://amazon.com/*",
    "*://api.listenbrainz.org/*",
    "*://api.trakt.tv/*",
    "*://atv-ps.amazon.com/*",
    "*://libre.fm/*",
    "*://music.youtube.com/*",
    "*://netflix.com/*",
    "*://open.spotify.com/*",
    "*://play.google.com/music/*",
    "*://radon.browser.local/*",
    "*://ws.audioscrobbler.com/2.0/*",
    "*://www.amazon.com/*",
    "*://www.netflix.com/*",
    "webRequest"
  ],
  "background": {
    "scripts": [
      "Common.js",
      "Background/Common.js",
      "Background/Messaging.js",
      "Background/Services/Callback.js",
      "Background/Services/ContentScript.js",
      "Background/Services/Library.js",
      "Background/Services/Scrobble.js",
      "Background/Services/App.js",
      "Background/Services/Migrate.js"
    ]
  },
  "content_scripts": [],
  "options_ui": {
    "page": "Application.html#/configuration",
    "browser_style": false,
    "open_in_tab": true
  },
  "web_accessible_resources": [
    "Application.html",
    "Plugins/amazonvideo/Shim.js",
    "Plugins/googlemusic/Shim.js",
    "Plugins/lastfm/Callback.html",
    "Plugins/librefm/Callback.html",
    "Plugins/netflix/Shim.js",
    "Plugins/spotify/Shim.js",
    "Plugins/trakt/Callback.html",
    "Plugins/youtubemusic/Shim.js"
  ]
}