feat: Update schema to support scanner dwi derivatives

[effigies]

Also closes bids-standard/bids-validator#12.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.54%. Comparing base (b8c98ec) to head (4f864c2).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    bids-standard/legacy-validator#2145      +/-   ##
==========================================
+ Coverage   85.72%   87.54%   +1.82%     
==========================================
  Files          91      133      +42     
  Lines        3782     7003    +3221     
  Branches     1220     1657     +437     
==========================================
+ Hits         3242     6131    +2889     
- Misses        454      777     +323     
- Partials       86       95       +9     

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