[docs] [issue30550] Document order-preserving dictionary output in json

[Karthikeyan Singaravelan]

Change by Karthikeyan Singaravelan <tir.karthi at gmail.com>:


----------
nosy: +rhettinger
versions: +Python 3.7, Python 3.8, Python 3.9 -Python 3.6

_______________________________________
Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue30550>
_______________________________________