Function kummer_function

# Kummer function ## Definition [Kummer function](https://en.wikipedia.org/wiki/Confluent_hypergeometric_function), is a generalized hypergeometric series defined by: $$ M(a,b,z) = \sum_{n=0}^{\infty}\frac{a^{(n)}z^n}{b^{(n)}n!} $$ ## Inputs - `a`: first parameter, will be computed in the rising factorial ($a$) - `b`: second parameter, will be computed in the rising factorial ($b$) - `x`: the va

(a: f64, b: f64, x: f64)