Examine source code of Simplicate monthly view

{
  "manifest_version": 2,
  "name": "Simplicate monthly view",
  "version": "1.0",
  "description": "Adds a monthly hours overview grouped by project to the Simplicate timesheet view (https://.simplicate.nl/hours/timesheet).",
  "icons": {
    "48": "icons/icon-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.simplicate.nl/hours/*"
      ],
      "js": [
        "js/jquery-3.4.1.min.js",
        "js/simplicate-monthly-view.js"
      ],
      "css": [
        "css/simplicate-monthly-view.css"
      ]
    }
  ]
}