Examine source code of autonomail

{
  "manifest_version": 3,
  "name": "autonomail",
  "version": "1.0",
  "description": "AutoNoMail – a blog dedicated to online marketing in general and Email Marketing in particular.",
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "images/icon16.png",
      "48": "images/icon48.png",
      "128": "images/icon128.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{657f04b1-375e-906d-b753-02f76e890e4d}"
    }
  }
}