Examine source code of Simple Screenshot

{
  "manifest_version": 2,
  "name": "Simple Screenshot",
  "version": "1.0",
  "description": "A simple screenshot extension. Icon by Freepik https://www.flaticon.com/free-icons/camera",
  "permissions": [
    "activeTab",
    "tabs",
    "downloads"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_icon": "photo_camera.png",
    "default_title": "Take Screenshot"
  },
  "commands": {
    "take-screenshot": {
      "suggested_key": {
        "default": "Alt+3"
      },
      "description": "Take a screenshot of the visible page"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{22e62413-bf80-4170-b40b-aac8b9f0ae83}"
    }
  }
}