Add an easier way to do json encoding

[mikeshultz]

JSON encoding doesn't work plainly right now. Though users can create custom implementations to handle it, it would be better to add a way to do easy json encoding so json.dumps() can be applied directly to results from a query.

[mikeshultz]

msgspec or pydantic? The latter may be too heavy for this, unless there's a nice way to just integrate the two.