FEATURE: advanced search option for max posts count (PR #10761)

This commit adds an option to search for max posts count and updates the UI for posts count search to show a min/max range in single line.

Before:

Screenshot 2020-09-28 at 8 02 22 PM

After:

Screenshot 2020-09-28 at 7 56 19 PM

GitHub

Trivial but the entities ‐ or — are probably better than this.