Non-standard prefix used for Argon2 algorithm

[antness]

Hello!

I am using your library for password hashing with the Argon2 algorithm. I've observed that the library uses 2id as the prefix for Argon2id hashes, which appears to deviate from widely accepted community practices that typically use $argon2id$. This could lead to compatibility issues with other systems that rely on the more common $argon2id$ prefix to recognize and validate Argon2id hashes.