create example notebooks for dandi

@bendichter - would it be possible to create a specific notebook example for DANDI? that includes a cell on top that downloads/instructs to download data using datalad? once we move all the dandisets to AWS, this should become much faster.

just like we pull in the nwb repo, we can pull this repo in whenever a user logs in to the dandi hub, so any changes to this repo will get picked up.

you could in fact create the examples in the hub, and then send a PR to this repo with those notebooks.