Scale Every Column to 0 and 1

A model that sees one feature in rupees and another as a ratio between 0 and 1 will be dominated by the rupees, for no reason other than scale. Min-max scaling is the cheapest fix and the one you write most often.

Write min_max_scale(x).

x is a 2D array of shape (n_rows, n_features). Return an array of the same shape where every column has been rescaled so its smallest value becomes 0.0 and its largest becomes 1.0.