Add adapter for vibe JSON

[NCrashed]

I loves optional fields feature, but having two different types of JSON is tedious in web projects. Is there a possibility to add sub configuration to use vibe.data.json instead of std.json?

P.S. If the feature is implemented, adding support vibe.data.bson would be a piece of cake to implement.

[rcorre]

I'm not familiar with vibe.data.json, though at first glance it looks like there is a decent amount of crossover. What would the use case here be? Using @jsonize style attributes to control how vibe serializes things?

This does bring up a good point: I'd like to separate jsonizer's logic into two parts:

1. Reflecting on serializeable types (identifying what members should be serialized and how)
2. Actually performing serialization.

This would allow the back-end serializer to be swapped out without changing the API or reflection logic.