Make the auto scroll code run again

`<SuggestionsOverlay>` was converted to hooks and the code which handles
scrolling to the (keyboard) selected suggestion item was moved from
`componentDidUpdate` to a `useEffect` with an empty dependency array
causing it to run only on mount instead of on every state change.

Removing the dependency array completely would bring back the original
behavior but running just when `focusIndex` is often enough, so that has
now been added to the (previously empty) dependency array.

Author: JakeHedman

src/SuggestionsOverlay.js

@@ -50,7 +50,7 @@ function SuggestionsOverlay({
     } else if (bottom > ulElement.offsetHeight) {
       ulElement.scrollTop = bottom - ulElement.offsetHeight
     }
-  }, [])
+  }, [focusIndex])
 
   const renderSuggestions = () => {
     const suggestionsToRender = Object.values(suggestions).reduce(