Adding loader for MDB-stem-synth dataset

[dsuedholt]

Description

Please include the following information at the top level docstring for the dataset's module mydataset.py:

• Describe annotations included in the dataset
• Indicate the size of the datasets (e.g. number files and duration, hours)
• Mention the origin of the dataset (e.g. creator, institution)
• Describe the type of music included in the dataset
• Indicate any relevant papers related to the dataset
• Include a description about how the data can be accessed and the license it uses (if applicable)

Dataset loaders checklist:

• Create a script in scripts/, e.g. make_my_dataset_index.py, which generates an index file.
• Run the script on the canonical version of the dataset and save the index in mirdata/indexes/ e.g. my_dataset_index.json.
• Create a module in mirdata, e.g. mirdata/my_dataset.py
• Create tests for your loader in tests/datasets/, e.g. test_my_dataset.py
• Add your module to docs/source/mirdata.rst and docs/source/table.rst
• Run black, flake8 and mypy (see Running your tests locally).
• Run tests/test_full_dataset.py on your dataset.
• Check that codecov coverage does not decrease.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.06%. Comparing base (9f797d2) to head (6f8ac77).
Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #639      +/-   ##
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+ Coverage   97.05%   97.06%   +0.01%     
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  Files          66       67       +1     
  Lines        7498     7537      +39     
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+ Hits         7277     7316      +39     
  Misses        221      221              

[genisplaja]

Hey @dsuedholt, great PR, very neat. Thanks for that! I am leaving few minor comments to make the docs render properly and to issue a small linting bug but LGTM.

[genisplaja]

LGTM :)

[genisplaja]

hello again @dsuedholt :) Thanks for your time. Once this minor thing is done, I think we can merge :) If you have the time, could you please do it soon so that the loader can be included in the release we have scheduled for this week? Thanks!!

[dsuedholt]

Thanks for the friendly and helpful review @genisplaja! Let me know if there's anything else you need for the release.

[genisplaja]

I think now this is ready to merge :) Thanks @dsuedholt for the contributing and the timely responses!