Examine source code of Text Prefix Number Panel

{
  "manifest_version": 2,
  "name": "Text Prefix Number Panel",
  "version": "1.0.0",
  "description": "Add a custom prefix number to each line.",
  "browser_action": {
    "default_title": "Prefix Number",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "text-prefix-number-915b5e41-be7d-41a8-8eef-3bf1bf7f23b1@example.com",
      "strict_min_version": "58.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}