Examine source code of YouTube Grabber

{
  "name": "__MSG_extensionName__",
  "description": "__MSG_appDesc__",
  "version": "0.9.3",
  "manifest_version": 2,
  "permissions": [
    "activeTab",
    "storage",
    "nativeMessaging",
    "downloads",
    "notifications",
    "*://www.youtube.com/*",
    "*://m.youtube.com/*",
    "*://*.googlevideo.com/*"
  ],
  "background": {
    "persistent": false,
    "scripts": [
      "/data/locale.js",
      "download.js",
      "ffmpeg.js",
      "common.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "16": "/data/icons/16.png",
      "32": "/data/icons/32.png",
      "64": "/data/icons/64.png",
      "128": "/data/icons/128.png",
      "256": "/data/icons/256.png",
      "512": "/data/icons/512.png"
    },
    "default_popup": "/data/popup/index.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*",
        "*://m.youtube.com/*"
      ],
      "js": [
        "data/inject/id.js",
        "data/inject/button.js"
      ],
      "css": [
        "data/inject/styles.css"
      ],
      "run_at": "document_start",
      "all_frames": false
    }
  ],
  "icons": {
    "16": "/data/icons/16.png",
    "32": "/data/icons/32.png",
    "64": "/data/icons/64.png",
    "128": "/data/icons/128.png",
    "256": "/data/icons/256.png",
    "512": "/data/icons/512.png"
  },
  "web_accessible_resources": [
    "/data/inject/download.svg",
    "/data/inject/panel/index.html"
  ],
  "options_ui": {
    "page": "data/options/index.html",
    "chrome_style": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8c53f6e6-d41e-4b8a-b901-21b47c97a1c9}"
    }
  }
}