Examine source code of Last.fm Dark Mode

{
  "manifest_version": 3,
  "name": "Last.fm Dark Mode",
  "version": "1.2.2",
  "description": "Turn Last.fm dark with this extension for a sleek, eye-friendly listening experience.",
  "icons": {
    "16": "darkfm.png",
    "48": "darkfm.png",
    "128": "darkfm.png"
  },
  "permissions": [],
  "host_permissions": [
    "*://*.last.fm/*"
  ],
  "action": {
    "default_icon": {
      "16": "darkfm.png",
      "48": "darkfm.png",
      "128": "darkfm.png"
    },
    "default_popup": "popup.html",
    "default_title": "Last.fm Dark Mode"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.last.fm/*"
      ],
      "css": [
        "darkmode.css"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "dark-mode-for-lastfm@example.com",
      "strict_min_version": "109.0"
    }
  }
}