missing method to fetch history of transfers for the margin account

[aleqx]

Unless I'm really missing something, it seems the library is missing a method to fetch the history of transfers for the margin account, i.e. a GET call to margin/transfer as described here https://binance-docs.github.io/apidocs/spot/en/#get-cross-margin-transfer-history-user_data

It has methods to perform a transfer from margin to spot, and vice versa.

Also seems to be missing methods for transferring from margin to/from coin-m and usd-m futures accounts (perhaps a better idea is to have a generic transfer method between accounts, where the source and destination accounts can be passed as parameters; same for a transfer history method).

Was all this intentional? if not then I might submit a PR