DOCSP-29114: API documentation summary (#366)

* DOCSP-29114: API documentation summary

Author: Chris Cho

source/api-documentation.txt

@@ -2,7 +2,18 @@
 API Documentation
 =================
 
-.. default-domain:: mongodb
+- `BSON <{+api+}/apidocs/bson/index.html>`__ - classes for working with the 
+  BSON data format.
+- `BSON Record Codec <{+api+}/apidocs/bson-record-codec/index.html>`__ - 
+  classes for encoding and decoding between Java records and the BSON data 
+  format.
+- `Core <{+api+}/apidocs/mongodb-driver-core/index.html>`__ - classes that
+  contain essential driver functionality.
+- `Java Driver (modern API) <{+api+}/apidocs/mongodb-driver-sync/index.html>`__ -
+  classes for the current driver API.
+- `Java Driver (legacy API) <{+api+}/apidocs/mongodb-driver-legacy/index.html>`__ -
+  classes that support the legacy driver API. To learn how to upgrade from the
+  legacy API to the modern API from the :ref:`<java-legacy-api>` documentation.
 
 .. toctree::
    :titlesonly:
@@ -13,4 +24,4 @@ API Documentation
     Core <{+api+}/apidocs/mongodb-driver-core/index.html>
     Java Driver (modern API) <{+api+}/apidocs/mongodb-driver-sync/index.html>
     Java Driver (legacy API) <{+api+}/apidocs/mongodb-driver-legacy/index.html>
-    
+