paymasterAddress is not required for sponsored transactions in the relay-kit

[DaniSomoza]

Context / issue

paymasterAddress in the Relay Kit is currently required by the types. But it is not actually required if you want to use sponsored Transactions.

Proposed solution

update the relay-kit types:

export type SponsoredPaymasterOption = {
  isSponsored: true
  paymasterUrl: string
  sponsorshipPolicyId?: string
}

export type ERC20PaymasterOption = {
  isSponsored: false
  paymasterAddress: string
  paymasterTokenAddress: string
  amountToApprove?: bigint
}

export type PaymasterOptions = SponsoredPaymasterOption | ERC20PaymasterOption | undefined