Better document usage of shot-based protocols

[madagra]

Currently, there is almost no documentation on how to use tomography and classical shadows protocols.

[Roland-djee]

Features to document into a "Realistic Simulations" section of the docs:

• [x] Measurements
• [x] Error models
• [x] Error mitigation

[madagra]

Yes, indeed. Thanks, @Roland-djee. This should be a priority and should be addressed directly with #128 or separately.