Returns the index of the first occurrence of a wide character in a slice,
None if the character is not found.
use wchar::wch; use wmemchr::wmemchr; let haystack = wch!(u16, "foo bar"); assert_eq!(wmemchr(wch!(u16, 'o'), haystack), Some(1)); assert_eq!(wmemchr(wch!(u16, 'z'), haystack), None);