Add custom chain from dApp

[shaqk]

Ability to have the dApp prompt the wallet to add a new chain

[aaroncox]

I think for this to be achievable as part of the Session Kit, we'd need a common standard that all wallets follow to allow the addition of a new chain.

Totally agree that this is needed, especially with IBC and sidechains picking up in popularity. Completing this task in the Session Kit is going to have a number of prereqs that need to be completed first 😅