STORM-3879: Add Kafka README files to distribution (#8435)

Author: MNkulkarni06

storm-dist/source/src/main/assembly/source.xml

@@ -38,5 +38,20 @@
                 <exclude>**/.lien.*/**</exclude>
             </excludes>
         </fileSet>
+        <fileSet>
+            <directory>../../external/storm-kafka-migration</directory>
+            <outputDirectory>/external/storm-kafka-migration</outputDirectory>
+            <includes>
+                <include>README.md</include>
+            </includes>
+        </fileSet>
+
+        <fileSet>
+            <directory>../../external/storm-kafka-monitor</directory>
+            <outputDirectory>/external/storm-kafka-monitor</outputDirectory>
+            <includes>
+                <include>README.md</include>
+            </includes>
+        </fileSet>
     </fileSets>
 </assembly>