Examine source code of Link Counter v11

{
  "manifest_version": 2,
  "name": "Link Counter",
  "version": "1.0",
  "description": "Counts all links on a page",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Count Links!"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{7d28195d-adc8-4508-a998-904ed88fff7b}"
    }
  }
}