Document advance usage for the preprocessing of the data when applying the RejectionPolicy

[christian-oreilly]

In #250, we demonstrate advance usage related to preprocessing when applying the pylossless annotations to the original data

Advanced: Custom Preprocessing

# Skip certain preprocessing operations
rejection_policy = ll.RejectionPolicy()
rejection_policy.preprocessing_operations_to_skip = ['notch_filter']
cleaned = rejection_policy.apply(pipeline)

# Override preprocessing parameters
rejection_policy.operation_param_overrides = {
    'filter': {'l_freq': 0.5, 'h_freq': 40.0}
}
cleaned = rejection_policy.apply(pipeline)

# Use original data without any preprocessing
rejection_policy.apply_preprocessing = False
original_with_artifacts_removed = rejection_policy.apply(pipeline)

This issue to adjust one of our tutorials (or add a new one) that demonstrates this "advanced" usage.