add missing wheel tooltip to rountangle editor

src/frontend/versioned_model.tsx

@@ -46,6 +46,7 @@ const helpText = {
   rountangleEditor: <>
     <Mantine.Text><b>Alt + Left-Click</b>: Create/Delete Rountangle</Mantine.Text>
     <Mantine.Text><b>Left-Drag</b>: Move/Resize Rountangle / Pan Canvas</Mantine.Text>
+    <Mantine.Text><b>Wheel</b>: Zoom</Mantine.Text>
   </>,
   depGraph: <>
     <Mantine.Text><b>Left-Drag</b>: Drag Node</Mantine.Text>