Examine source code of Focus Blur Mode

{
  "manifest_version": 2,
  "name": "Focus Blur Mode",
  "version": "1.0",
  "description": "Blur the page except for an area around the mouse cursor to help focus.",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "permissions": [
    "activeTab",
    "tabs",
    "storage",
    "<all_urls>"
  ],
  "browser_action": {
    "default_title": "Focus Blur Mode",
    "default_icon": "icons/icon-48.png",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_script.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{3c78d171-465e-4a0d-a1e3-a42e4e5a2f74}"
    }
  }
}