Examine source code of DistractionBlocker

{
  "manifest_version": 2,
  "name": "DistractionBlocker",
  "version": "1.0",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "index.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ee071f58-ef83-4005-87dc-1e83f6b8fa71}"
    }
  }
}