Serializing to bytes

[davetapley]

In the spirit of #450 I'd like to propose a feature to optionally serialize JSON to bytes.

However: pyserde supports both json and orjson (here), and json says:

The json module always produces str objects, not bytes objects.

So: How do you feel about a serializer which would do .encode('utf-8') in the absence of orjson,
and use orjson.dumps otherwise?

[yukinarit]

Hi @davetapley
I am fine with adding such an optional parameter to to_json!

[davetapley]

Great! I'll get a PR in ASAP.