add fscore, reorganize mod and change error in doc.

[tsanona]

Pull Request Template

Checklist

• Confirmed that run-checks all script has been executed.
• Made sure the book is up to date with changes in this PR.

Related Issues/PRs

#544

Changes

Add F_(β)ScoreMetric
Reorganize metric\mod to mach existing order.

Testing

Added tests for new metric

[codecov]

Codecov Report

Attention: Patch coverage is 90.27778% with 7 lines in your changes missing coverage. Please review.

Project coverage is 81.85%. Comparing base (7a19b5f) to head (79541d0).

Files with missing lines	Patch %	Lines
crates/burn-train/src/metric/fscore.rs	90.27%	7 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2648   +/-   ##
=======================================
  Coverage   81.84%   81.85%           
=======================================
  Files         838      839    +1     
  Lines      107487   107559   +72     
=======================================
+ Hits        87975    88040   +65     
- Misses      19512    19519    +7     

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