Make a guide for adding a new L2

[OisinKyne]

Problem to be solved

We want to enable hundreds of L2s to be able to deploy a trustless local RPC in a single line of code. For some we can do it by example, but a workflow for replicating this will make it easy for all L2s to ship this way.

Proposed solution

Start simple, make a guide. Include FAQs. This pr #19 is a first attempt at such a thing.

We need to add these RPCs to eRPC. and maybe the front end can pick up and display the eRPC config.

[OisinKyne]

Linea charts to try and levrage: https://github.com/Consensys/ethereum-helm-charts