feat: nanoGPT example

[alexander-camuto]

Here we add nanoGPT as an example to the repo. We leverage divide-by rather than multiply-by rescaling to accomodate large model depth and chained linear layers.

to run nanoGPT mock test:

cargo test --release --verbose tests::large_mock_::large_tests_1_expects

to run the full test:

cargo test --release --verbose tests::large_kzg_prove_and_verify_::large_tests_1_expects

thanks to @biancaganescu for helping make this happen :)