Examine source code of YouTube UI Toggle

{
  "manifest_version": 2,
  "name": "YouTube UI Toggle",
  "version": "1.0",
  "description": "Toggles the YouTube UI with Ctrl+Q",
  "permissions": [
    "activeTab",
    "storage",
    "tabs",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "commands": {
    "toggle-ui": {
      "suggested_key": {
        "default": "Ctrl+Q"
      },
      "description": "Toggle YouTube UI"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{05b18dce-9e24-44e4-883c-9e1df24921ad}"
    }
  }
}