ninja-fix - adding an extra space to render the page correctly with mkdocs

I've been looking into details on custom codes and noticed that the there is an issue with rendering bullet points on the following page: https://apache.github.io/cassandra-java-driver/4.19.0/core/custom_codecs/

Author: MikeLaptev

manual/core/custom_codecs/README.md

@@ -33,6 +33,7 @@ Define custom Java to CQL mappings.
         (MutableCodecRegistry) session.getContext().getCodecRegistry();    
     registry.register(myCodec);
     ```
+
 * using a codec:
   * if already registered: `row.get("columnName", MyCustomType.class)`
   * otherwise: `row.get("columnName", myCodec)`