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

[Eric O. LEBIGOT]

Changes by Eric O. LEBIGOT <eric.lebigot at normalesup.org>:


----------
assignee:  -> docs at python
components: +Documentation -Library (Lib)
nosy: +docs at python

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