Examine source code of Snake Game Extension

{
  "name": "Snake Game Extension",
  "description": "A snake game with leaderboard in a popup.",
  "version": "1.0",
  "manifest_version": 3,
  "action": {
    "default_popup": "index.html",
    "default_icon": {
      "16": "icon16.png",
      "48": "icon48.png",
      "128": "icon128.png"
    }
  },
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "permissions": [
    "storage"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "snake-gamextension@example.com"
    }
  }
}