Examine source code of sync.js

{
  "manifest_version": 2,
  "name": "sync.js",
  "version": "2.3",
  "description": "The easy way to transfer data.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "main.html",
    "default_icon": {
      "48": "icon.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "sjs@sync-js.pages.dev"
    }
  }
}