Add support for the new IBC Transfer memo field

[nicolaslara]

IBC recently introduced an optional memo field into the ICS20 FungibleTokenTransfer packet data (docs).

To support this in cosmwasm, it would need to be added to IBCMsg::Transfer as an Option<String> and to the matching encoder in wasmd.

The code changes to add this are relatively simple; the complexity is in coordinating the release on wasmd and cosmwasm-std and making this works well across the different versions.

[webmaster128]

Hey @nicolaslara. Thanks for bringing that up. I think this is a duplicate of #1477. Feel free to add any thoughts to this ticket.

[nicolaslara]

Ahh, thanks! didn't notice that one... I think I only searched in wasmd.