parses a string literal public key into a byte array public key
§Arguments
input - A public key string
§Examples
use static_pubkey::static_pubkey;
let key = static_pubkey!("GjphYQcbP1m3FuDyCTUJf2mUMxKPE3j6feWU1rxvC7Ps");
assert!(key.to_string() == "GjphYQcbP1m3FuDyCTUJf2mUMxKPE3j6feWU1rxvC7Ps");