Overlay DA neighborhoods on embedding

[mdmanurung]

Is your feature request related to a problem? Please describe.
When working with large datasets, visualisation of the DA neighborhoods take such a long time. Subsetting the neighborhoods helps, but then it's difficult to relate the results with the embedding layout.

Describe the solution you'd like
I suggest to provide an option to overlay the DA neighborhoods on top of the embedding, like what I did below:

If you think this approach make sense, I am more than happy to make a pull request.