Function artha::neural_net::sigmoid

pub fn sigmoid<T>(arr: &Array2<T>) -> Array2<f64> where
    T: Copy,
    f64: From<T>, 

Loops through the Array and calculates sigmoid of each value.

Note: Since taking the sigmoid of each value in the matrix requires it to be converted to floating point and From f64 trait is not implemented for i32/64 nor for u32/64/size, this function returns f64 Array