feat(server): Add resolver to flag Brain Initiative datasets

[nellh]

Initial resolver to provide a searchable list of datasets annotated with "Brain Initiative" in the BIDS Funding fields or the OpenNeuro metadata field.

[codecov]

Codecov Report

Attention: Patch coverage is 38.29787% with 29 lines in your changes missing coverage. Please review.

Project coverage is 47.02%. Comparing base (25a7401) to head (5651a9c).

Files with missing lines	Patch %	Lines
...ro-server/src/graphql/resolvers/brainInitiative.ts	34.14%	27 Missing ⚠️
packages/openneuro-server/src/graphql/schema.ts	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3315      +/-   ##
==========================================
- Coverage   47.03%   47.02%   -0.02%     
==========================================
  Files         583      584       +1     
  Lines       36954    37001      +47     
  Branches     1174     1174              
==========================================
+ Hits        17382    17400      +18     
- Misses      19385    19414      +29     
  Partials      187      187              

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