navigate through search results within a note

### What
I am not sure there is a way (or at least an obvious way) to navigate through the search results within a note in the Mac app. When I search in the search bar, all the matching notes show up. Within each note, I can see the relative location of the search results highlighted in the scroll bar area, but I have to manually scroll within the note to see them.

### Why
This exists in the web app. There are arrows in the bottom right corner that will navigate through all the matches within a note. I believe this was the relevant issue: https://github.com/Automattic/simplenote-electron/issues/983

### How
This is already implemented in the web app.

Inspect the macOS app's search results and note view, then compare the existing web-app behavior described in issue 983. The work is done when arrows let users move through every match within the selected note, matching the web app's navigation behavior.

Written by the indexing model from the issue text.