Examine source code of Responsive Fix

{
  "manifest_version": 2,
  "name": "Responsive Fix",
  "version": "1.1",
  "description": "Mejora la visualización de sitios antiguos en móviles",
  "permissions": [],
  "data_collection_permissions": {
    "required": [
      "none"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "responsive-fix-listed@local",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "style.css"
      ],
      "run_at": "document_idle"
    }
  ]
}