use Uniswap on optimism to perform swaps

Example Flow:

- User deposits 1000 DAI into the DCA contract on L1 and intends to buy 100 DAI worth of ETH every week
- DCA contract bridges the 1000 DAI over to L2
- DCA L2 contract uses uniswap on L2 to swap the DAI for ETH
- After 10 weeks, all the DAI is converted into ETH on L2
- User withdraws the ETH from L2 back into L1