Make track settings dialog modal

This is the only way to get the correct role=dialog on it. Otherwise it
always has role=tooltip and we can't change it. See https://github.com/yjose/reactjs-popup/blob/4d8e41a5995ba5074c0133bf0901bf0f93805616/src/index.tsx#L280 and yjose/reactjs-popup#334

src/components/TrackSettingsButton.js

@@ -10,7 +10,7 @@ export const TrackSettingsButton = ({
     availableColors
 }) => {
     return(
-        <Popup trigger={<button type="button"> Settings </button>} position="right center"> 
+        <Popup trigger={<button type="button"> Settings </button>} position="right center" modal> 
             <TrackSettings 
             fileType={fileType}
             trackColorSettings={trackColorSettings}