Feature: Add data_dir optional argument to Huggingface DataLoader

[Pablo1785]

Add data_dir optional argument to Huggingface DataLoader to enable some manual download use cases

Pull Request Template

Checklist

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

Related Issues/PRs

#2811

Changes

Some datasets (e.x. facebook/covost2) require this argument to include the subset of the dataset downloaded manually.

Testing

./run_checks.sh all

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 11 lines in your changes missing coverage. Please review.

Project coverage is 81.69%. Comparing base (2c4c039) to head (a823fe8).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
.../burn-dataset/src/source/huggingface/downloader.rs	0.00%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2817      +/-   ##
==========================================
- Coverage   81.69%   81.69%   -0.01%     
==========================================
  Files         851      851              
  Lines      113982   113993      +11     
==========================================
  Hits        93122    93122              
- Misses      20860    20871      +11     

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[laggui]

LGTM! Thanks for addressing the issue yourself 🙏