A contract wrapper

[tobowers]

Hello! Thanks for merging my PR. I also just made this: https://github.com/quorumcontrol/kasumah/tree/main/packages/kasumah-multicall and I'm wondering if it makes sense for me to merge that code into this repo too.

Basically that code allows you to create an app singleton that will handle using Multicall for you... you just wrap your contracts and that package takes care of batching up the requests and returning them to you using Multicall.