Optimize webpack bundle

[dohaki]

Besides creating a commonjs and esmodule with tsc, we also create a bundle using webpack. Problem is that the bundle size is 1.61 MB and has to be reduced.

[cducrest]

Maybe reduce the size of contracts.json by filtering the contracts that end up in it. That could solve it, but check if maybe also ether.js is too big ...

[cducrest]

Maybe check if ethers is too big and newer versions are smaller?