Typo in README of confusion_matrix, and suggestion to specify valid values for `normalize`

[dantp-ai]

In the Output Values section are some typos:

"""
Minimum possible value is 0. Maximum possible value is 1.0,
or the number of examples input, if normalize is set to True.
"""

The corrections are in bold:

"""
Minimum possible value is 0. Maximum possible value is 1.0,
or the number of examples in the input, if normalize is set to None (default).
"""

Additionally, I would specify in the Inputs section the permitted values for normalize: {'pred', 'all', 'true'} or None.