Examine source code of mailTabler

{
  "manifest_version": 2,
  "name": "mailTabler",
  "description": "makes it easy to create, edit and manage tables in your gmail emails",
  "version": "1.0.0",
  "permissions": [
    "activeTab"
  ],
  "icons": {
    "64": "icons/logo.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.google.com/*"
      ],
      "js": [
        "content_script.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{53d2df9f-325a-4715-8e68-d762f7f7be50}"
    }
  }
}