Make an enum to type TransactionInfo.status

[decentraliser]

I think it would make sense for the SDK to type TransactionInfo.status with an enum.
Then we could use this enum in REST and clients as well

https://github.com/nemtech/nem2-sdk-typescript-javascript/blob/4bb78e62297b09dc8e3d460bbc4645396eee92fe/src/model/transaction/TransactionStatus.ts#L33-L36