CI to make small datasets for interoperability testing

[kevinyamauchi]

We should make small datasets with all elements represented available for interoperability testing (e.g., can all elements be loaded into R or Vitessce)

[LucaMarconato]

No need to cover all the functionalities but the majority of it.

[LucaMarconato]

The CI is ready but it is not running every night. We need to:

• [ ] enable the nightly runs.

Also, @HelenaLC

• [ ] asked if we can include the blobs and raccoon datasets there. I'll do it.

[HelenaLC]

Was thinking also the raccoon, if possible (unless you got rid of that?) - basically anything that's in the notebooks should be findable somewhere, I think :)