Examine source code of Word Counter v11

{
  "manifest_version": 2,
  "name": "Word Counter",
  "version": "1.0",
  "description": "Counts words on any webpage",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Count Words!"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{57f6f46e-f8c6-4957-8f3f-09152cf53506}"
    }
  }
}