rusty_paseto vulnerable to private key extraction due to ed25519-dalek dependency

Summary

## Impact

The vulnerability, known as RUSTSEC-2022-0093, impacts the `ed25519-dalek` crate, which is a dependency of the `rusty-paseto` crate. This issue arises from a "Double Public Key Signing Function Oracle Attack" affecting versions of `ed25519-dalek` prior to v2.0. These versions expose an unsafe API for serializing and deserializing 64-byte keypairs that include both private and public keys, creating potential for certain attacks. `d25519-dalek` users utilizing these serialization and deserialization functions directly could potentially be impacted.

## Patches

The vulnerability within the `ed25519-dalek` crate has been addressed in version 2.0. `rusty-paseto` has addressed it in release v0.6.0.

## Workarounds

Users are recommended to upgrade to v0.6.0 of `rusty-paseto`. However, users should still ensure that their key serialization and deserialization practices are secure and avoid any practices that could lead to key exposure.

## References

More information about RUSTSEC-2022-0093 can be found in the [RustSec Advisory Database](https://rustsec.org/advisories/RUSTSEC-2022-0093.html). Updates and details regarding the upcoming release of `rusty-paseto` will be documented in the project's [releases](https://github.com/your-repo/rusty-paseto/releases) and [changelog](https://github.com/your-repo/rusty-paseto/blob/main/CHANGELOG.md). This issue was first reported by Dependabot on 2023-08-15. The source was reviewed by @rrrodzilla at that time and a determination was made that the vulnerability low harm to existing users due to the strongly typed nature of keys provided by the rusty-paseto API. @techport-om reported the vulnerability to the repository by discovering during a `cargo-audit` run on 2023-11-05 and opened [issue 28](https://github.com/rrrodzilla/rusty_paseto/issues/28). This advisory was created at that time to notify existing users.