Need to update the DIFFICULTY opcode (now PREVRANDAO after the merge)

[karmacoma-eth]

See https://eips.ethereum.org/EIPS/eip-4399

I'm happy to contribute updated EVM reference docs if that's helpful

[dorlevi]

@karmacoma-eth, quick update:

@thevaizman picked this up (trying his first FE contribution); besides updating the reference, we also wanted to ensure the playground has support for the opcode/new behavior and updating to the latest Etherjs, which sadly introduced a bug with our playground so we want to give it a few days to see what they say.

[thevaizman]

@karmacoma-eth another update on the status of this issue:

While I managed to patch their source code and run the build locally and test that everything is working fine, I ran into some problems building the app using the new version of the @ethereumjs/evm library that causes build errors.
I opened yet another issue on their Github, and I am now waiting for the devs response.
Will update as soon as this gets resolved.

[thevaizman]

@karmacoma-eth After a long wait, due to multiple issues we had with our major external dependency, we can finally close this issue as it was addressed in this PR.

Sorry it took so long :)