Examine source code of WTM Random Letter Picker

{
  "manifest_version": 3,
  "name": "WTM Random Letter Picker",
  "version": "1.0",
  "description": "A simple and easy-to-use Random Letter Picker extension.",
  "action": {
    "default_popup": "popup.html"
  },
  "icons": {
    "16": "assets/images/icon-16.png",
    "32": "assets/images/icon-32.png",
    "48": "assets/images/icon-48.png",
    "128": "assets/images/icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "wtmrandomletterpicker_webmateapp@gmail.com"
    }
  }
}