Add debug view to App component

frontend/src/App.tsx

@@ -249,6 +249,21 @@ function App(): JSX.Element {
             height={thumbnailHeight}
           />
         </div>
+        <ul style={{ listStyleType: 'none' } as React.CSSProperties}>
+          <li>Frames: {mediaSet.audioFrames}</li>
+          <li>
+            Viewport (frames): {viewport.start} to {viewport.end}
+          </li>
+          <li>
+            Selection (frames): {selection.start} to {selection.end}
+          </li>
+          <li>
+            Position (frames):{' '}
+            {Math.round(mediaSet.audioFrames * (position.percent / 100))}
+          </li>
+          <li>Position (seconds): {position.currentTime}</li>
+          <li></li>
+        </ul>
       </div>
     </>
   );