Added custom writetime

Author: faizalrub-datastax

README.md

@@ -70,3 +70,4 @@ spark.destination.autocorrect.mismatch                  true|false
 - SSL Support (including custom cipher algorithms)
 - Migrate from any Cassandra source ([Apache Cassandra](https://cassandra.apache.org)/[DataStax Enterprise (DSE)](https://www.datastax.com/products/datastax-enterprise)/[DataStax Astra DB](https://www.datastax.com/products/datastax-astra)) to any Cassandra target ([Apache Cassandra](https://cassandra.apache.org)/[DataStax Enterprise (DSE)](https://www.datastax.com/products/datastax-enterprise)/[DataStax Astra DB](https://www.datastax.com/products/datastax-astra))
 - Validate migration accuracy and performance using a smaller randomized data-set
+- Custom writetime