updateExchangeLink() Function

[drewroberts]

This function updates the exchange link variable in the contract. By default it is just https://app.uniswap.org/swap

[drewroberts]

This function is not in my old contract standard. There should simply be an exchangeLink variable that is set to https://app.uniswap.org/swap. This function would allow that to be updated by the contract owner to our DEX link.