add capi blobstore interactions doc to sidebar
add capi blobstore interactions doc to sidebar

[https://www.pivotaltracker.com/story/show/165781280]

Authored-by: Connor Braa <e624947c8d30070ca3f5f65daa9bdf76de21947b@pivotal.io>

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