Add web socket connection with op-node

[avalonche]

op-node can connect to rollup-boost over a ws:// connection instead of http:// one.

in the non-flashblocks world, op-node's engine rpc can be set as a ws://url-of-op-geth. So to keep things consistent it would be a nice to have it done the same way against rollup-boost

[SozinM]

Working on this

[SozinM]

Right now we are using
ProxyLayer as http middleware to handle everything
To make it websocket compatible we will need to rewrite it to use RpcModule, then we will get websocket + http out of the box