Add function to download MaStR data from Zenodo

[gplssm]

Download cleaned data from Zenodo.

Fixes #14

[gplssm]

Hey @ClaraBuettner,
I added some code for download of data from Zenodo and linked it in the pipeline.
I chose to download only "cleaned" data for now. But this can be configured in the function. Remember, cleaned data is the same as raw data, just filtered (the definition will change).
I didn't do more than providing the CSV files. Can you work with or do have other things that I should do here?

And for reference: https://open-mastr.readthedocs.io/en/dev/data_documentation.html#

[ClaraBuettner]

Thank you, I can work with this!
It is still marked as draft, does that mean that you currently don't want to merge this?

[gplssm]

Thank you, I can work with this!

😎

It is still marked as draft, does that mean that you currently don't want to merge this?

At least I wanted to discuss with you first.
Since you seem happy with this as intermediate solution, I would be ok to merge it to dev and create a new issue for adding post-processing or simply download post-processed MaStR data later.

I add a note to the CHANGELOG and make the PR ready for review then.