Generalized inverse of a tensor is missing
The generalized inverse of a Matrix defined by https://en.wikipedia.org/wiki/Moore%E2%80%93Penrose_inverse.

The function is usually called ``pinv``(Numpy, Scipy, Julia LinAlg, Octave) sometime ``ginv`` (R).
For reference : https://docs.scipy.org/doc/scipy/reference/generated/scipy.linalg.pinv.html (source : https://github.com/scipy/scipy/blob/v1.6.0/scipy/linalg/basic.py#L1288-L1305)


I would be a useful addition I think (could add it to https://github.com/mratsim/Arraymancer/issues/58 ).