Examine source code of Text Word Initial Counter

{
  "manifest_version": 2,
  "name": "Text Word Initial Counter Panel",
  "version": "1.0.0",
  "description": "Count how many words start with each letter.",
  "browser_action": {
    "default_title": "Initial Counter",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "text-word-initial-counter-34aa363e-f728-44bf-9174-2b05bf021dd3@example.com",
      "strict_min_version": "58.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}