Examine source code of YouTube Configurator

{
  "manifest_version": 2,
  "name": "YouTube Configurator",
  "version": "1.0.5",
  "description": "Configurate YouTube's (unwanted) behaviours with functions not listed in the settings page",
  "icons": {
    "48": "icons/icon_48.png",
    "96": "icons/icon_96.png"
  },
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "default_icon": {
      "32": "icons/icon_32.png"
    },
    "default_title": "YouTube Configurator",
    "default_popup": "popup/index.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{9fd60e91-dd4e-4895-81a9-b6aa459d9397}"
    }
  }
}