Examine source code of Youtube viewer

{
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "{d5970ac0-2c7c-453d-af91-b660bd64f88b}",
      "strict_min_version": "52.0"
    }
  },
  "name": "__MSG_extensionName__",
  "version": "1.4.5",
  "default_locale": "en",
  "description": "__MSG_extensionDesc__",
  "icons": {
    "128": "icons/128.png",
    "256": "icons/256.png"
  },
  "web_accessible_resources": [
    "icons/*.png",
    "listener.js"
  ],
  "browser_action": {
    "default_icon": "icons/128.png"
  },
  "options_ui": {
    "page": "index.html#settings",
    "open_in_tab": true
  },
  "background": {
    "page": "index.html#background"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "static/js/browser-polyfill.min.js",
        "content.js"
      ]
    }
  ],
  "author": "AXeL-dev",
  "homepage_url": "https://github.com/AXeL-dev/youtube-viewer",
  "content_security_policy": "script-src 'self' https://www.google-analytics.com/ https://www.youtube.com/ https://s.ytimg.com; object-src 'self'; child-src https://www.youtube.com/ https://s.ytimg.com",
  "permissions": [
    "storage",
    "notifications",
    "tabs",
    "contextMenus"
  ]
}