SnakeCase

Create a SnakeCase<T> generic that turns a string formatted in camelCase into a string formatted in snake_case.

A few examples:

type res1 = SnakeCase<"hello">; // => "hello"
type res2 = SnakeCase<"userName">; // => "user_name"
type res3 = SnakeCase<"getElementById">; // => "get_element_by_id"