Update StorageEngineOverview.md
Update StorageEngineOverview.md

Add a TL;DR at the top so people can quickly know what to do.
couchbase/couchbase-lite-net,brettharrisonzya/couchbase-lite-net,brettharrisonzya/couchbase-lite-net,couchbase/couchbase-lite-net,couchbase/couchbase-lite-net