Examine source code of WPlace Darkmode

{
  "manifest_version": 3,
  "name": "WPlace Darkmode Button",
  "version": "1.0",
  "description": "Adds a button to wplace.live to switch between dark and light mode.",
  "content_scripts": [
    {
      "matches": [
        "https://wplace.live/*"
      ],
      "js": [
        "button-darkmode.js"
      ],
      "run_at": "document_end"
    }
  ],
  "icons": {
    "16": "icons/icon.png",
    "32": "icons/icon.png",
    "48": "icons/icon.png",
    "128": "icons/icon.png"
  },
  "author": "Enea",
  "homepage_url": "https://github.com/Frenxys",
  "browser_specific_settings": {
    "gecko": {
      "id": "wplace-darkmode-button@frenxys.github"
    }
  }
}