[ENH] Add "Keywords" to dataset_description.json

[markmikkelsen]

Keywords are standard in publications. Including them in BIDS as optional metadata will hopefully increase the visibility of datasets (perhaps this is something that can also be added to OpenNeuro).

[effigies]

This seems sensible to me.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.71%. Comparing base (4411fde) to head (f4233b9).
⚠️ Report is 30 commits behind head on master.

Additional details and impacted files

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  Coverage   82.71%   82.71%           
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  Files          20       20           
  Lines        1608     1608           
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  Hits         1330     1330           
  Misses        278      278           

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[neuromechanist]

This is a very nice addition.
I wonder if at a later date and PR, we'd want to consider a list of suggested keywords, which can be quite easily derived from semantic analysis of the current datasets?