Examine source code of Factorial+

{
  "manifest_version": 2,
  "name": "Factorial+",
  "version": "1.0.3",
  "description": "Unofficial extension that aims to add some little useful features to factorialhr.com",
  "author": "Josep Marí",
  "default_locale": "en",
  "icons": {
    "32": "icons/icon-32.png",
    "64": "icons/icon-64.png",
    "128": "icons/icon-128.png",
    "256": "icons/icon-256.png"
  },
  "permissions": [
    "*://*.factorialhr.com/*",
    "tabs",
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.factorialhr.com/*"
      ],
      "js": [
        "lib/moment.min.js",
        "lib/jquery-3.4.1.min.js",
        "src/utils/module-utils.js",
        "src/utils/date-utils.js",
        "src/module-loader.js",
        "src/modules/add-calendar-info.js",
        "src/modules/week-totals.js",
        "src/modules/show-only-current-week.js"
      ],
      "css": [
        "styles/variables.css"
      ]
    }
  ],
  "web_accessible_resources": [
    "styles/*"
  ],
  "background": {
    "scripts": [
      "background/tab-listener.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{1e062ace-ba50-41f2-b66d-b156b00bb03a}"
    }
  }
}