Examine source code of numino-Borderify

{
  "manifest_version": 2,
  "name": "Borderify",
  "version": "1.0",
  "description": "Adds a red border to all webpages matching mozilla.org.",
  "icons": {
    "128": "icons/logo.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.mozilla.org/*"
      ],
      "js": [
        "borderify.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{d083b9fd-7b68-4717-9a7a-bc6cfc3a8088}"
    }
  }
}