MINOR: add upgrade note for KIP-173 topic configs

Author: Damian Guy <damian.guy@gmail.com>

Reviewers: Matthias J. Sax <matthias@confluent.io>, Guozhang Wang <wangguoz@gmail.com>

Closes #3921 from dguy/minor-kip-173-docs

docs/streams/upgrade-guide.html

@@ -118,7 +118,6 @@
             Note: the previous aggregate functions on <code>KGroupedStream</code> still work, but have been deprecated.
         </li>
     </ul>
-
     <p>
         Modified methods in <code>Processor</code>:
     </p>
@@ -149,6 +148,16 @@
         Detailed metrics sensor can be found in the <a href="#kafka_streams_monitoring">Streams Monitoring</a> section.
     </p>
 
+    <p>
+        The introduction of <a href="https://cwiki.apache.org/confluence/display/KAFKA/KIP-173%3A+Add+prefix+to+StreamsConfig+to+enable+setting+default+internal+topic+configs">KIP-173</a>
+        enables you to provide topic configuration parameters for any topics created by Kafka Streams.
+        This includes repartition and changelog topics.
+        You can provide the configs via the <code>StreamsConfig</code> by adding the configs with the prefix as defined by <code>StreamsConfig#topicPrefix(String)</code>.
+        Any properties in the <code>StreamsConfig</code> with the prefix will be applied when creating internal topics.
+        Any configs that aren't topic configs will be ignored.
+        If you already use <code>StateStoreSupplier</code> or <code>Materialized</code> to provide configs for changelogs, then they will take precedence over those supplied in the config.
+    </p>
+
     <h3><a id="streams_api_changes_0110" href="#streams_api_changes_0110">Streams API changes in 0.11.0.0</a></h3>
 
     <p> Updates in <code>StreamsConfig</code>: </p>