Turn into class component and hook kernelspy

[Carreau]

If we want to have the kernelspy handler to control the papyri browser from the outside, we need to turn the functional component into a class one for access the methods instead of having closures.

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Create component ref and hook into the kernelspy.

This using the IPython extension and using ? on an existing object, it
should pop out the right docstring.

%load_ext papyri

import numpy as np
np.einsum?