feat: add basic file ocr and contributing

[LongxingTan]

Description

This PR ...

Checklist

• Linked issues (if existing)
• Amended changelog.md for large changes (and added myself there as contributor)
• Added/modified tests
• Used pre-commit hooks when committing to ensure that code is compliant with hooks. Install hooks with pre-commit install.
  To run hooks independent of commit, execute pre-commit run --all-files

Thank you for joining. Have fun coding!

[codecov]

Codecov Report

Attention: Patch coverage is 39.13043% with 42 lines in your changes missing coverage. Please review.

Project coverage is 55.84%. Comparing base (df31d6e) to head (02ca40d).

Files	Patch %	Lines
src/retrievals/models/embedding_auto.py	8.00%	23 Missing ⚠️
src/retrievals/data/collator.py	23.07%	10 Missing ⚠️
src/retrievals/data/dataset.py	68.96%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #65      +/-   ##
==========================================
+ Coverage   54.53%   55.84%   +1.31%     
==========================================
  Files          30       30              
  Lines        2417     2462      +45     
==========================================
+ Hits         1318     1375      +57     
+ Misses       1099     1087      -12     

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