* docs: Fix typo in doc for categorical transformer.
* feat: Add option to take a column from Matrix.
I created the method `Matrix::take_column` that uses the `Matrix::take`-interface to extract a single column from a matrix. I need that feature in the implementation of `StandardScaler`.
* feat: Add `StandardScaler`.
Authored-by: titoeb <timtoebrock@googlemail.com>
