"Add Network" -- directly add network to wallet's network list via rpc

[youfoundron]

Requires a prior wallet connection, depends on #22

interface example: https://chainlist.org/

code example: https://github.com/FrederikBolding/chainlist/blob/9feb9b3e8ffc4044385bdebcee0696262dcd3a45/src/context/Web3Context.tsx#L39-L47

[youfoundron]

This applies to Avalanche, Celo, & FLOW -- anything else?