Constant BASE32_NOPAD

Unpadded base32 encoding

This encoding is a static version of:

# use data_encoding::{Specification, BASE32_NOPAD};
let mut spec = Specification::new();
spec.symbols.push_str("ABCDEFGHIJKLMNOPQRSTUVWXYZ234567");
assert_eq!(BASE32_NOPAD, spec.encoding().unwrap());