Add tx creator for swaps in exchange subgraph

[yabirgb]

Request

Uniswap updated their subgraph for V2 adding an extra field from https://github.com/Uniswap/uniswap-v2-subgraph/blob/master/schema.graphql#L201 that contains the EOA that initiated the txn. Add this field to the sushiswap subgraph

Reason

When obtaining trades for an account in order to create a report we've found that there are transactions send to the account but created by a different address. In that cases this transaction shouldn't be considered but without that field is not possible to do this.