Examine source code of No Focus Outlines

{
  "manifest_version": 2,
  "name": "No Focus Outlines",
  "version": "0.1.3resigned1",
  "description": "Disables focus outlines for all elements.",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "author": "Rotem Dan",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "nofocusoutlines.css"
      ],
      "run_at": "document_start",
      "all_frames": true
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{606e17b3-7cd4-43a4-b61f-66337b5b06eb}"
    }
  }
}