feat: allow for custom ids passed in through a config

[ByteAtATime]

This PR adds a pretty neat feature: the possibility to include multiple burner connectors at once.

Previously, we would pass in the connector like this:

const wallets = [metaMaskWallet, rainbowkitBurnerWallet];

Now, you can pass in a custom id parameter, allowing you to simultaneously have two burner wallets in the same app. For example:

const wallets = [
  metaMaskWallet.
  rainbowkitBurnerWallet, // backwards compatible!
  rainbowkitBurnerWallet({ id: "burner-1", name: "Burner Wallet #1" }),
  rainbowkitBurnerWallet({ id: "burner-2", name: "Burner Wallet #2", storageKey: "custom-localstorage-private-key" }),
]

The id parameter is used by wagmi to differentiate between different connectors, as well as for storing the private key (by default, it stores the key in localStorage at {id}.pk). The localStorage key can be overridden using the storageKey field.

[ByteAtATime]

Just thought of this: should we have something that tracks the registered IDs, to make sure there are no duplicates?