Examine source code of Mister Overlay

{
  "manifest_version": 3,
  "name": "Mister Overlay",
  "version": "0.1.0",
  "description": "Adds value trend and last-season points onto the Mister (Mundo Deportivo) market and player views.",
  "browser_specific_settings": {
    "gecko": {
      "id": "mister-overlay@urip.dev",
      "strict_min_version": "128.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    },
    "gecko_android": {}
  },
  "content_scripts": [
    {
      "matches": [
        "https://mister.mundodeportivo.com/*"
      ],
      "js": [
        "src/inject.js"
      ],
      "css": [
        "src/overlay.css"
      ],
      "run_at": "document_start"
    }
  ]
}