Examine source code of Text Word Length Analyzer

{
  "manifest_version": 2,
  "name": "Text Word Length Analyzer Panel",
  "version": "1.0.0",
  "description": "Analyze average word length in text.",
  "browser_action": {
    "default_title": "Word Length",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "text-word-length-7f3a9c9a-76d5-40d5-9857-91fbb59c64fd@example.com",
      "strict_min_version": "58.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}