Optimize release

Features

• Added + support

let value = ms("+100").unwrap();
assert_eq!(value, 100)

• Now ms supported only one whitespace between number and postfix

let value = ms("100 ms").unwrap(); // valid
assert_eq!(value, 100)

let value = ms("100  ms").unwrap(); // invalid
assert_eq!(value, 100)

Optimizes

• Now it works on 2x faster! (from 16ns to 8ns)