Author: M^0 Labs
The interface as defined by EIP-1271: https://eips.ethereum.org/EIPS/eip-1271
Returns a specific magic value if the provided signature is valid for the provided digest.
Parameters
digest
bytes32
Hash of the data purported to have been signed.
signature
bytes
Signature byte array associated with the digest.
Returns
magicValue
bytes4
Magic value 0x1626ba7e if the signature is valid.