feat: add output root rpc method

[ncitron]

The Optimism specs for the rollup client include a special RPC method called optimism_outputAtBlock which returns the L2 output root for a given block number. This is used by the proposer component to post the outputs to L1. While we're a long way away from connecting Magi to the proposer, we can pretty easily support this. Lets use the jsonrpsee crate for this.

More info on the RPC method here

[shrimalmadhur]

@ncitron I am down to give this a try. I am not that familiar with rust and just starting but definitely would be able to help. :) Let me know if there is any specific guidance for it apart from the crate you mentioned

[ncitron]

That would be great. When you implement this, can we make a new top level module called rpc and put the logic there (then start it from the driver module).

[shrimalmadhur]

Okay. on it. might have more questions later. but I am good to start.