Search filter

**DocFX Version Used**: 2.35.4

**Template used**: default

**Steps to Reproduce**:

1. generate with basic options

**Expected Behavior**: have ability to apply filter to top search

**Actual Behavior**: I don't see a mechanism for this in the documentation

I'm a newbie so I could have easily missed it... Looking at the Microsoft Dynamics docs they have a way to apply a filter in the top search box. Is this a custom post-processing step they've done - or did I just not see it in the FxDoc documentation?