Verify operations caching

[nebarf]

Adding an optional caching layer when decoding JWTs should provide a performance boost on application level since servers tend to process same tokens multiple times.

The idea could be to implement such layer based on a LRU cache with a configurable capacity. Also the cache TTL should take into account time-sensitive claims (i.e. nbf, exp and iat) to guarantee the verification is retried when a token expires or becomes valid.

[Keats]

That's something that should be done by the app, not by the library.