adds index link for new topic
adds index link for new topic

cloudfoundry/docs-book-cloudfoundry,swisscom/docs-appcloud-book,swisscom/docs-appcloud-book,swisscom/docs-appcloud-book,cloudfoundry/docs-book-cloudfoundry,cloudfoundry/docs-book-cloudfoundry,swisscom/docs-appcloud-book,cloudfoundry/docs-book-cloudfoundry