`addChain` should return if a chain is already supported

> So what im seeing now is that we are using the useChains hook, with some chains in there that are already in my Keplr wallet, but still they pop up as if they are new chains and need to be added to Keplr as new chain

https://github.com/cosmology-tech/cosmos-kit/blob/d5f38a315a29b5672f83504038ee083467c5ba3e/wallets/keplr-extension/src/extension/client.ts#L123-L140

for now, only do keplr mobile and keplr extension, you can leverage JSON from

https://github.com/cosmos/wallet-registry/blob/8a644ef3d1cadbb8ab240b969d381d07b79897e0/wallets/keplrextension/wallet.json#L8C3-L35C5

https://github.com/cosmos/wallet-registry/blob/8a644ef3d1cadbb8ab240b969d381d07b79897e0/wallets/keplrmobile/wallet.json#L8C2-L46C20