conf.json

{
  "base_template": "classic",
  "mimetypes": {
    "text/html": true
  },
  "preprocessors": {
    "100-pygments": {
        "type": "nbconvert.preprocessors.CSSHTMLHeaderPreprocessor",
        "enabled": true
    },
    "500-reveal": {
      "type": "nbconvert.exporters.slides._RevealMetadataPreprocessor",
      "enabled": true
    }
  }
}