calling createTransaction without a name creates an invalid transaction

[Drew Cain]

createTransaction does not validate the name parameter: https://github.com/denodrivers/postgres/blob/main/client.ts#L200

As a result on subsequent calls to the transaction an error is returned that the transaction is not open because the name is undefined: https://github.com/denodrivers/postgres/blob/main/query/transaction.ts#L157