Function change_case::lower_case

pub fn lower_case(input: &str) -> String

Change to lower case

use change_case::lower_case;
assert_eq!(lower_case(""), "");
assert_eq!(lower_case("test"), "test");
assert_eq!(lower_case("TEST"), "test");
assert_eq!(lower_case("test string"), "test string");
assert_eq!(lower_case("TEST STRING"), "test string");