added the air.cab into a random location in the ditamap so that issue #29 can be demonstrated

Author: SmartLayer

src/smartlayer-docsite.ditamap

@@ -18,6 +18,7 @@
   <topicref href="usecase/UseCaseOverview.md" format="mdita">
     <topicref href="usecase/case-study/CaseStudy1.md" format="mdita"/>
     <topicref href="usecase/case-study/CaseStudy2.md" format="mdita"/>
+    <topicref href="usecase/guide/air.cab.md" format="mdita"/>
   </topicref>
   <!--
   <topicref href="integration/IntegrationGuide.md" format="mdita"/>