Add MBIS multipole electrostatics example notebooks

[harshjha15335]

Summary

This PR adds two example Jupyter notebooks demonstrating the use of FFprime's MBIS atomic multipole electrostatics workflow for computing and visualizing electrostatic potentials.

Added
examples/multipole_water.ipynb
Loads a water molecule from an .fchk file.
Computes MBIS atomic multipoles.
Evaluates electrostatic potentials using:
monopoles only
full multipole expansion (monopole + dipole + quadrupole)
Visualizes both potentials and their difference using contour plots.
examples/multipole_peptide.ipynb
Applies the same workflow to a peptide fragment.
Demonstrates how higher-order multipoles modify the electrostatic potential in a chemically more realistic system.
Implementation
Exposed MBIS atomic dipoles and quadrupoles through the partitioning pipeline so they are available from Nonbonded.
Included the required example input files:
examples/water.fchk
examples/peptide.fchk
Purpose

These notebooks provide reproducible examples of FFprime's multipole electrostatics workflow and visually illustrate the difference between monopole-only and full multipole electrostatic potentials.

[harshjha15335]

@ccastilloo