Examine source code of DSL.sk-DarkMode

{
  "manifest_version": 2,
  "name": "DSL.sk-DarkMode",
  "version": "1.0",
  "applications": {
    "gecko": {
      "id": "podpora@tpsoft.org"
    }
  },
  "description": "Dark Mode for DSL.sk",
  "icons": {
    "48": "images/logo-48.png",
    "96": "images/logo-96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.dsl.sk/*"
      ],
      "js": [
        "js/jquery-3.4.1.min.js",
        "js/main.js"
      ]
    }
  ]
}