Allow scalar figure vmin/vmax to be percentiles

[tsalo]

Changes proposed in this pull request

• Modify plot_scalar_map to allow the vmin and vmax values to be percentile strings (e.g., 98%).
• Change one of the scalar maps' settings to use the new feature.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 12.82%. Comparing base (d0325f4) to head (c3cd383).

Files with missing lines	Patch %	Lines
qsirecon/interfaces/reports.py	0.00%	19 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #314      +/-   ##
==========================================
- Coverage   12.85%   12.82%   -0.03%     
==========================================
  Files          56       56              
  Lines        7951     7966      +15     
  Branches     1089     1093       +4     
==========================================
  Hits         1022     1022              
- Misses       6897     6912      +15     
  Partials       32       32              

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