Document HyperGraph Capabilities

I noticed in this issue https://github.com/microsoft/GraphEngine/issues/245 that GraphEngine is able to support HyperGraph structures. I can't find the documentation on these features. This [SO Post](https://stackoverflow.com/questions/58711840/recommendation-for-hypergraph-dbms-with-visual-editor-or-at-least-viewer) shows that people cannot find a good HG engine.