feat: add RBFE tutorial for comparing protein conformations

- Introduced a new Jupyter notebook `rbfe_open_closed.ipynb` that sets up relative binding free energy (RBFE) calculations for two protein conformations: open (`3a7r`) and closed (`1x2h`).
- The tutorial demonstrates how to efficiently compare ligand binding across these conformations using a shared ligand network.
- Included detailed markdown explanations and code cells for configuration, ligand selection, and alignment processes, enhancing usability and clarity for users.

Author: FridrichMethod