Add BayesWHAM driver and configuration examples

[arminshzd]

Summary

• add a BayesWHAM driver that reuses the WHAM ingestion/iteration logic with Bayesian resampling for 1D and 2D trajectories
• expose a YAML configuration builder and CLI entry point plus library exports
• document BayesWHAM usage alongside a sample configuration file

Testing

• PYTHONPATH=src python -m pywham.bwham examples/bwham_config.yaml (interrupted for time)

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Codex Task