implement utils.document.tokenize_document

[ArneBinder]

taken from from pie_modules.document.processing. This implements #462.

[codecov]

Codecov Report

❌ Patch coverage is 91.07143% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.84%. Comparing base (4de30aa) to head (9b69976).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/pytorch_ie/utils/document.py	91.07%	2 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #497      +/-   ##
==========================================
- Coverage   76.34%   69.84%   -6.50%     
==========================================
  Files          31       31              
  Lines        1750     1804      +54     
  Branches      329      346      +17     
==========================================
- Hits         1336     1260      -76     
- Misses        337      474     +137     
+ Partials       77       70       -7     

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