Enable Taproot (BIP86 P2TR) for Foundation Passport

[mjg-foundation]

As in the title, when connecting the passport to specter, the BIP86 P2TR derivation should be available to import. Here's an example of our current taproot export using the electrum format:

1731cab2-specter-001.json

If our format needs to change, for example to use descriptors, I can update it to match your expected input.

Thanks!