Due to "popular" demand, I have created a BIP for cross chain atomic
transfers.

Unlike the previous version, this version only requires hash locking.   The
previous version required a "selector" transaction based on if statements.

    OP_HASH160 OP_EQUAL_VERIFY [public key] OP_CHECKSIG

    OP_HASH160 OP_EQUAL_VERIFY OP_N [public key 1] ... [public key m]
OP_M OP_CHECK_MULTISIG

https://github.com/TierNolan/bips/blob/bip4x/bip-atom.mediawiki