Examine source code of Nofollow Link Highlight

{
  "manifest_version": 2,
  "name": "Nofollow Link Highlighter",
  "version": "1.0",
  "description": "Highlights nofollow links on web pages.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icon.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{0739ec9a-6106-40d5-82e2-e7620538a26a}"
    }
  }
}