add graph neural networks

[zshiqiang]

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[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (a3d128d) 91.67% compared to head (72b9f65) 92.55%.

❗ Current head 72b9f65 differs from pull request most recent head 26b8522. Consider uploading reports for the commit 26b8522 to get more accurate results

Files	Patch %	Lines
.../omlt/io/torch_geometric/torch_geometric_reader.py	99.17%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #110      +/-   ##
==========================================
+ Coverage   91.67%   92.55%   +0.88%     
==========================================
  Files          29       32       +3     
  Lines        1730     1948     +218     
  Branches      327      373      +46     
==========================================
+ Hits         1586     1803     +217     
  Misses         74       74              
- Partials       70       71       +1     

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[rmisener]

Thanks for making all the changes! Excited about this PR.