Add CellRank?

[lazappi]

What do people think about adding CellRank to velociraptor? It is a tool that uses velocities (from scVelo usually) to identify root and end states and calculate transition probabilities. More details here https://cellrank.readthedocs.io/en/latest/.

It is available on pip/conda and has a similar API to scVelo so I think it should be fairly straightforward. If people are interested I'm happy to start on a PR, if not I might look at making a separate package.

[LTLA]

That can be done, but I would like to see the current state pushed into BioC first, there's enough moving parts as it is.