[Feature Request]Provide support for Parity Signer or at least ability to manually perform the staking transaction

[ramast]

Background:
Right now to use Rocket Pool for staking you need either metamask or wallet connect to start.
Both options can be compromised unless the user owns a hardware wallet.

So basically a hardware wallet is currently necessary to use your service when staking more than 1 ETH

Problem

• Some countries don't allow crypto so users may not want to disclose that they own crypto.
• Hardware wallet could be replaced by a fake one en-route to the user among other issues.

Proposal:

Add support for an air gaped wallet like Parity Signer or Air Gap.
If that is not possible, at least allow advanced users to perform the transaction on their own using whatever wallet they use