Examine source code of A test extension

{
  "manifest_version": 3,
  "name": "A test extension",
  "version": "3.0.0",
  "permissions": [
    "activeTab"
  ],
  "action": {
    "default_title": "This is the title of a test extension"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "a-test-extension@will.drnd.me"
    }
  },
  "icons": {
    "512": "yellow.png"
  }
}