Max UUID as `MAX` constant

[broofa]

See §5.10.

We just need to add a MAX constant akin to how we provide NIL currently.

[github-actions]

Marking as stale due to 90 days with no activity.

[LinusU]

PR to implement this: #714

Currently the validate function does not consider the MAX uuid as valid, maybe this is something we want to change in the next major version? 🤔