DOCSP-37932: prev versions link (#25)

Author: rustagir

source/index.txt

@@ -18,6 +18,7 @@ MongoDB Java Reactive Streams
    /reference/
    View the Source <https://github.com/mongodb/mongo-java-driver>
    API Documentation <{+api+}/mongodb-driver-reactivestreams/>
+   Previous Versions <https://mongodb.github.io/mongo-java-driver/>
 
 Introduction
 ------------
@@ -39,6 +40,8 @@ runnable project by following one of the tutorials.
 
 - `API Documentation <{+api+}/mongodb-driver-reactivestreams/>`__
 
+- `Previous Versions Documentation <https://mongodb.github.io/mongo-java-driver/>`__
+
 If you need to make synchronous calls between your application and MongoDB, use
 the :driver:`MongoDB Java Driver </java/sync/current/>` instead of the
 {+driver-short+}.