Examine source code of Last.fm Reworked

{
  "manifest_version": 2,
  "name": "Last.fm Reworked",
  "version": "1.5.0",
  "description": "Enhances the Last.fm layout and user interface.",
  "icons": {
    "128": "icons/icon128.png"
  },
  "permissions": [
    "storage",
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://www.last.fm/*",
        "*://last.fm/*"
      ],
      "css": [
        "variables.css",
        "icons.css",
        "links.css",
        "content.css"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{1c52c611-5d1c-4cc4-91f2-2ac2f3da5d70}",
      "strict_min_version": "91.0"
    }
  }
}