Examine source code of ItsLoggedIn

{
  "manifest_version": 2,
  "name": "ItsLoggedIn",
  "version": "0.0.1",
  "icons": {
    "16": "blue16.png",
    "48": "blue48.png",
    "128": "blue128.png"
  },
  "description": "Disables auto log out for ItsLearning",
  "content_scripts": [
    {
      "matches": [
        "https://*.itslearning.com/*"
      ],
      "js": [
        "Content.js"
      ]
    }
  ]
}