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 97.45%. Comparing base (87eea28) to head (51064f3).
Report is 65 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1302      +/-   ##
==========================================
- Coverage   97.61%   97.45%   -0.16%     
==========================================
  Files          40       40              
  Lines        8685     8777      +92     
==========================================
+ Hits         8478     8554      +76     
- Misses        207      223      +16     

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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.