Examine source code of Blockify

{
  "manifest_version": 2,
  "name": "Blockify",
  "version": "1.1.1",
  "description": "Blocks Youtube during work hours",
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "blockify.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": {
      "16": "icons/icon-16.png",
      "32": "icons/icon-32.png",
      "48": "icons/icon-48.png",
      "96": "icons/icon-96.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{251a9018-e3f8-4524-aa03-403f6b3bf8b6}"
    }
  }
}