Document the how the arrays are handled in pyamtrack

[grzanka]

It would be good to include good documentation with several use cases to show how the arrays are handled in pyamtrack.
This requires:

• adjusting documentation of the wrapped functions. See i.e. https://libamtrack.github.io/docs/python/API/stopping/electron_range . Now the models and materials can be lists for example.
• adding a new page called for example "array handling" , maybe under Usage (https://libamtrack.github.io/docs/python/usage) which on some good cases explain possible options, like array+list, many arrays, higher dimensionality arrays etc...

[grzanka]

I had a nice experience with this simple code:

from pyamtrack.converters import beta_from_energy
print(beta_from_energy(150))

# 2D numpy array of energy, 200 MeV in the center, 10 MeV close to the edges, use some shape inside, like gaussian, the table should be 1000x1000

import numpy as np

energy = np.zeros((1000, 1000))
x0, y0 = 500, 500
sigma = 100
energy += 10  # Set the background energy
energy[x0-3*sigma:x0+3*sigma, y0-3*sigma:y0+3*sigma] += 190 * np.exp(-((np.arange(-3*sigma, 3*sigma)[:, None]**2 + np.arange(-3*sigma, 3*sigma)**2) / (2*sigma**2)))    

import matplotlib.pyplot as plt
plt.imshow(energy, cmap='hot', interpolation='nearest')
plt.colorbar(label='Energy (MeV)')
# add iso contours for every 20 MeV
plt.contour(energy, levels=np.arange(0, 201, 20), colors='white', linewidths=0.5)
# add labels for contours
plt.clabel(plt.contour(energy, levels=np.arange(0, 201, 20), colors='white', linewidths=0.5), inline=True, fontsize=8)
plt.title('Energy Distribution')
plt.xlabel('X Position')
plt.ylabel('Y Position')

beta = beta_from_energy(energy)
plt.imshow(beta, cmap='viridis', interpolation='nearest')
plt.colorbar(label='Beta')
# add iso contours for every 0.1
plt.contour(beta, levels=np.arange(0, 1.1, 0.1), colors='white', linewidths=0.5)
# add labels for contours
plt.clabel(plt.contour(beta, levels=np.arange(0, 1.1, 0.1), colors='white', linewidths=0.5), inline=True, fontsize=8)