feat: node diff

[zobront]

Most chain differences are presented in a user friendly way on evmdiff. There are cases where it's useful to see the actual diffs in the node, in order to see how these changes are implemented or understand edge cases.

Optimism has a very nice interface for exploring these differences: https://op-geth.optimism.io/

It's generate by this tool by protolambda: https://github.com/protolambda/forkdiff

Assuming all these chains have a geth fork as an implementation, it would be nice to be able to view these diffs for all pairs of chains (or, at the very least, each chain vs ETH mainnet).

Per @mds1, this would require tracking each chain's node repo in addition to the chain ID, but I believe it's a worthwhile feature.