Scroll Bar Highlights missing in Preview Mode Search Results

### Expected

When searching in edit mode, blue indicators appear in the scroll bar area to highlight which lines have the search word. In preview mode, the words are highlighted, and expected blue indicators in the scroll bar area.

### Observed

The scroll bar indicators do not appear in preview mode.

### Reproduced

Web app (app.simplenote.com) on Windows Chrome Version 89.0.4389.114 64-bit and Firefox 87.0. Replicated on any note.

### Where did you see the bug

Dell XPS 8300 Windows 64bit
Windows 10 Home, Version 10.0.19041 Build 19041
Windows Chrome Version 89.0.4389.114 64-bit and Firefox 87.0
Simplenote online (app.simplenote.com)

Reproduce the issue in the Simplenote web app on Windows Chrome or Firefox by searching a note in preview mode, then compare the scroll bar indicators with edit mode. Trace the preview-mode search-results rendering and identify where highlighted words are handled; done means matching blue scroll bar indicators appear in preview mode without changing edit-mode behavior.

Written by the indexing model from the issue text.