Constant vanityaddr::USAGE

pub(crate) const USAGE: &str = r#"
Usage: vanityaddr [OPTIONS] <PREFIX> <PREFIX> ...

Arguments:
  <PREFIX>    Prefixes to search

Options:
  -c    Make the search case-sensitive
  -t    Number of threads to use (defaults to number of available CPUs)
  -A    Search for an address
  -C    Search for a Contract ID
  -T    Search for a Token ID
"#;