PASETO Versions 3 and 4

[paragonie-security]

PASETO v3/v4 have been specified. The PASETO specification now lives here: https://github.com/paseto-standard/paseto-spec

The rationale for V3/V4 is worth reviewing.

We also updated our Implementation Guide and filed issues with other libraries to make sure Algorithm Lucidity is addressed, but JPaseto already did this, so you didn't hear from us. Good job ;)

(I'm sure this is already on your radar, but we've found having an issue somewhere is helpful.)