CI: add BIDS schema validator

[sappelhoff]

PR Description

• xref: Getting ready for schema based bids-validator #1288

Trying to add the schema validator to our CI

Merge checklist

Maintainer, please confirm the following before merging.
If applicable:

• All comments are resolved
• This is not your own PR
• All CIs are happy
• PR title starts with [MRG]
• whats_new.rst is updated
• New contributors have been added to CITATION.cff
• PR description includes phrase "closes <#issue-number>"

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.47%. Comparing base (ed75468) to head (c50032c).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1302   +/-   ##
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  Coverage   97.47%   97.47%           
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  Files          40       40           
  Lines        8872     8872           
=======================================
  Hits         8648     8648           
  Misses        224      224           

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[sappelhoff]

Okay, so as expected, we are getting a number of failures. Will be worth looking into that and fixing it.

Most importantly:

• [ERROR] ASSOCIATED_EMPTY_ROOM 'AssociatedEmptyRoom' field needs to point to an existing file.
• [ERROR] ENTITY_NOT_IN_RULE Entity not listed as required or optional for files with this suffix /sub-01/ses-01/meg/sub-01_ses-01_task-testing_run-01_markers.sqd - run not in rule rules.files.raw.meg.markers
• BTI data seemingly producing: [ERROR] NOT_INCLUDED Files with such naming scheme are not part of BIDS specification.