pub fn hrp_expand(hrp: &str) -> Vec<u8> ⓘExpand description
BIP 173-style HRP-expansion: produces the 5-bit-symbol prelude that gets prepended to the data part before running the BCH polymod.
For each HRP character c, emits c >> 5 (high 3 bits); then emits a
single 0 separator; then emits each character’s c & 31 (low 5 bits).
The result has length 2 * hrp.len() + 1 for ASCII HRPs.
For hrp_expand("md") this returns [3, 3, 0, 13, 4].