Makes a copy of the value in its ASCII lower case equivalent.
ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', but non-ASCII letters are unchanged.
To lowercase the value in-place, use [`make_ascii_lowercase`].
[`make_ascii_lowercase`]: Self::make_ascii_lowercase
# Examples
Basic usage:
```
# use ::exint::primitive::*;
# ::exint::uint! {
let uppercase_a = 65_u8;
let lowercase_a = 97_u8;
assert_eq!(lowercase_a, uppercase_a.to_ascii_lowercase());
# }
```