Examine source code of Native Speak Selection

{
  "manifest_version": 2,
  "name": "Speak Selection",
  "version": "1.0",
  "description": "Adds a context menu option to speak the selected text using the built-in speech synthesis normally reserved for reader mode.",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "16": "icons/speech.svg",
    "32": "icons/speech.svg",
    "48": "icons/speech.svg",
    "64": "icons/speech.svg"
  },
  "permissions": [
    "menus"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{baa6e348-a2ca-4783-8a7a-f8ff03dfa88d}"
    }
  }
}