Fetch taker and maker fee from relayer

[fvictorio]

Use /order_config endpoint to obtain the fees.

[dekz]

const orderConfigRequest: OrderConfigRequest = {
        exchangeAddress,
        makerAssetData,
        takerAssetData,
        makerAssetAmount,
        takerAssetAmount,
        makerAddress,
        takerAddress: NULL_ADDRESS,
        expirationTimeSeconds: new BigNumber(Math.floor((new Date().valueOf() / 1000) * 1.1)),
    };
    const orderResult = await client.getOrderConfigAsync(orderConfigRequest);
    const order = {
        ...orderConfigRequest,
        ...orderResult,
        salt: new BigNumber(new Date().valueOf()),
    };
    const signedOrder = await signatureUtils.ecSignOrderAsync(provider, order, order.makerAddress);
    await client.submitOrderAsync(signedOrder);