Add `sort_dicts` option

[joaonc]

From issue here: wolever#26
Existing PR here: wolever#27

In python 3.8, the sort_dicts option was added (here) and would be great to add that option in this package as well, not only to maintain drop replacement functionality with pprint, but also to add the functionality that argument brings.

[peter-malcolm-bw]

Thanks for forking and merging. Have you been able to take ownership of the project PyPi (https://pypi.org/project/pprintpp/) as part of the fork? It looks like the latest release is still 0.4.0 . Or is the plan to release under pprintpp2 or pprintppp ;) ?

[joaonc]

Hi @peter-malcolm-bw , I contacted @wolever, pprintpp's creator, to see if I can be added as admin in his project. If yes, then I'll merge back the changes done here and pprintpp will live on. Otherwise I'll start pprintpp2 as a replacement, which I've noticed is a common practice with open source projects that continue where others left off. Let's see what happens.