save era5 and xbt data to azure

[stevehadd]

In order to make the notebooks work as seamlessly as possiblt, we should create a copy of the XBT and ER5 data loaded in the notebooks to azure storage, as accessing the data on AWS S3 requires AWS credentials (its public, but you need to have credentials), which I expect most participants will not have. The XBT data is fairly small, and we can pick a subset of era 5 data to copy.

[stevehadd]

we should also demonstrate getting data from the copernicus data store.
https://cds.climate.copernicus.eu/api-how-to

[stevehadd]

create a zarr file from the downloaded era5 data to demonstrate how it is different to netcdf5 and better for cloud data acess.

[stevehadd]

this is now working. The notebooks do not contain the secret key, so we might need to think about a better long term solution. created #16 to look into that so closing this issue.