Function softmax

pub fn softmax<A, S, D>(args: &ArrayBase<S, D>) -> Array<A, D>
where
    A: Float + ScalarOperand,
    D: Dimension,
    S: Data<Elem = A>,

Softmax function: $f(x_i) = \frac{e^{x_i}}{\sum_j e^{x_j}}$