Feature request: add Cerebro files exporting capability

[erzakiev]

Hello i came across your package and i think it's amazing!
I think it could fit nicely in our lab's standard toolbox. It fills the missing link between the scRNAseq raw data and our local instance of a Cerebro server, which we use extensively with to do data exploration and visualisation. Up until this moment I was in charge of converting raw scRNAseq data into the .crb files that Cerebro can understand, but your app seems to do exactly that!!
Can I request a feature upgrade: ability to export .crb files from ShIVA? These are really just .RDS files with certain characteristics and this is done with the original package cerebroApp

[erzakiev]

Adding a pull merge pull request #3. Note that I didn't test the resulting docker file because i had no space on my disk unfortunately