Examine source code of Lichess Dark Mode

{
  "manifest_version": 2,
  "name": "Lichess Dark Mode",
  "version": "1.2.0",
  "description": "Sitewide dark mode for Lichess with a clean graphene palette.",
  "author": "kyriakosdt",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icons/icon-48.png",
      "96": "icons/icon-96.png"
    },
    "default_title": "Lichess Dark Mode"
  },
  "content_scripts": [
    {
      "matches": [
        "https://lichess.org/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start",
      "all_frames": false
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "lichess-dark-mode@kyriakosdt",
      "strict_min_version": "91.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "web_accessible_resources": [
    "styles/main.css",
    "icons/icon-48.png",
    "icons/icon-96.png"
  ]
}