Examine source code of First Letter Extractor

{
  "manifest_version": 2,
  "name": "Text First Letter Extractor Panel",
  "version": "1.0.0",
  "description": "Extract the first letter of each word in a text.",
  "browser_action": {
    "default_title": "First Letter Extractor",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "text-first-letter-af28b3db-8d2a-400f-ae9e-944e6e5f27fd@example.com",
      "strict_min_version": "58.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}