update documentation for eigengame and Parallel

[steelec]

documentation should be added to the wiki for these tools for

1. Eigengame implementation
2. Parallel
3. and, .ipynb example with comparison to standard PCA (toy example)

Wiki stub created here: https://github.com/neuralabc/NeuralABC_tools/wiki/Eigengame

for ipynb, use the tests subdirectory: https://github.com/neuralabc/NeuralABC_tools/tree/main/NeuralABC_tools/tests