Add wallet adapter for NuFi

[gyorgy-kurucz-vacuum]

This adds support for the upcoming NuFi extension.

(The interface is based on Phantom's, they should be compatible, except for changing the window.solana key to window.nufiSolana of course.)

[jordaaash]

Hey, I want to address the lack of activity on your PR. Thank you for your patience!

Here's a followup on the state of wallet-adapter, the issues that individual adapters have in getting integrated with applications, and how we intend to improve things: #384 (comment)

Let's discuss in that thread to keep it in one place.

[jordaaash]

While the medium-term goal is to move away from requiring adapters for every wallet, I want to respect the time you took to create this adapter, and review it now.

Once a new standard is introduced, let's work together to migrate away from dependency on using an adapter.

[gyorgy-kurucz-vacuum]

Thank you for the review, feel free to point out if there are any other redundant parts left as a result of copying the Phantom code that I didn't catch.

[jordaaash]

Thanks! This will be published today or tomorrow.

[jordaaash]

Published! https://twitter.com/jordaaash/status/1541927694786600961