[5.5] Added Argon2 Hash Support

[BenExile]

This adds the ability to use the Argon2 hashing algorithm. This implementation has the following dependencies:

• PECL libsodium >= 2.0.0
• libsodium >= 1.0.9

This allows earlier adoption of the Argon2 hashing algorithm, rather than waiting for PHP 7.2 stability, and the implementation can be changed to support the core extension later on.

[taylorotwell]

Release it as a package, please. When PHP 7.2 is available we can add support for it.

[Dylan-DPC-zz]

You can look at: https://github.com/koenhoeijmakers/laravel-argon2

[BenExile]

@Dylan-DPC Thanks. I thought I'd send a PR for this to be in core as PHP 7.2 hasn't reached a stable release yet. This would allow Laravel to support Argon2 ahead of that release, with no additional packages, and probably much earlier than 7.2.* is used in production for many applications.