docs(notebooks): add M3 readout error mitigation guide

[kevinsung]

Summary

Notebook explaining readout error and how to mitigate it for the Sampler primitive using mthree.

Details and comments

[coveralls]

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[ritajitmajumdar1]

This is a great notebook to teach M3. However, a few points which I felt:

1. Is it possible to choose a different example? For this example, the mitigated outcome is not a quasi-distribution. So anyone who is not aware of this will have a hard time understanding the requirement of nearest_probability_distribution.
2. Is is possible to show the outcome of each of the three steps - read the mapping, calibrate, and mitigate. The outcome of mitigation is already shown as a histogram. But can you also show the outcomes of read (I guess here it will be the first two qubits), and calibrate also? Drives in the point of calibration running only on relevant qubits.