Examine source code of Focus Mode for YouTube

{
  "manifest_version": 2,
  "name": "Focus Mode for YouTube",
  "version": "1.2",
  "author": "Cesar Carrillo",
  "description": "",
  "icons": {
    "48": "icons/icon-48x48.png"
  },
  "permissions": [
    "storage",
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "script.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": {
      "38": "icons/icon-38x38.png"
    },
    "default_title": "Focus Mode Settings",
    "default_popup": "settings.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{4ab72cb4-3378-4032-86ea-bf39338829eb}"
    }
  }
}