[Buildroot] package/python-orjson: new package

[Graeme Smecher]

The python-orjson package is: [1]

	"[...] a fast, correct JSON library for Python. It benchmarks as
	the fastest Python library for JSON and is more correct than the
	standard json library or other third-party libraries. It
	serializes dataclass, datetime, numpy, and UUID instances
	natively."

For buildroot (at least for my purposes), the ability to efficiently
serialize numpy arrays is the distinguishing feature from other Python
JSON libraries (of which, simplejson, json, and ujson are already
packaged here.)

1: https://pypi.org/project/orjson/

Signed-off-by: Graeme Smecher <gsmecher at threespeedlogic.com>