function asMinimalOP(buffer) {
  if (buffer.length === 0) return OPS.OP_0;
  if (buffer.length !== 1) return;
  if (buffer[0] >= 1 && buffer[0] <= 16) return OP_INT_BASE + buffer[0];
  if (buffer[0] === 0x81) return OPS.OP_1NEGATE;
}
Converts a minimal script buffer to its corresponding opcode, if applicable.

@param buffer - The buffer to check.
@returns The corresponding opcode or undefined if not minimal.