Examine source code of widen-mail

{
  "manifest_version": 2,
  "name": "widen-mail",
  "version": "1.0",
  "description": "Removes the annoying blank sidebar on the right side of Outlook.com",
  "content_scripts": [
    {
      "matches": [
        "*://*.outlook.live.com/*"
      ],
      "js": [
        "./main.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{504431f0-9ba0-4b48-8f1a-61c8c8ec2903}"
    }
  }
}