add dns prereqs topic to front page[#139251363]
add dns prereqs topic to front page[#139251363]

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