Refund request is improperly documented

[johndavi]

Good to see the Shippo hygiene is in good stead here, noting my three month old unresponded-to bug right below this one.

    res = s_client.refunds.create(request={
        "transaction": "abcdefg",
        "async_": False,
    })

This is incorrect and the library instead expects kwargs for this request.

res = shippo_sdk.refunds.create(
                    transaction="abcdefg"
                    async_=False
                )