Update preface.adoc

Fix list of supported databases

Author: gavinking

documentation/src/main/asciidoc/reference/preface.adoc

@@ -12,7 +12,8 @@ is represented using a chain of Java ``CompletionStage``s or Mutiny ``Uni``s and
 Java persistence frameworks like JDBC, JPA and Hibernate ORM were designed to use blocking IO for interaction with the
 database, and are therefore not appropriate for use in a reactive environment. As far as we know, Hibernate Reactive
 is the first true ORM implementation designed to take advantage of non-blocking database clients. Out of the box, the
-Vert.x clients for PostgreSQL, MySQL, and DB2 are supported, though the architecture is not limited to these drivers.
+Vert.x clients for PostgreSQL, MySQL, DB2, SQL Server, Oracle, and CockroachDB are supported, though the architecture 
+is not limited to these drivers.
 
 This programming paradigm holds the potential for improved scalability, and more controlled degradation under peak load,
 in some runtime scenarios. However, in general, one should not expect to see an immediate performance gain in all