Support importing/exporting keys from/to Paserk

[not-my-profile]

In order to use Paseto for my application I need cross-language interoperability. However the only two Paseto v4 implementations for Python enforce Algorithm Lucidity, meaning they currently cannot be easily used in conjunction with this library, since it doesn't support Paserk.

So it would be great if this library could support importing/exporting keys from/to Paserk :)

To be specific I'm talking about the local, public and secret PASERK types from this matrix.

[panva]

https://github.com/panva/paseto/releases/tag/v3.1.0