Improve measure example ux

- Pass click events on measure tooltips through to the map
- Put the tooltip for  the currently drawn geometry on top
- Disable text selection in the tooltips so clicking to draw does not select

examples/measure.js

@@ -248,6 +248,8 @@ function createMeasureTooltip() {
     element: measureTooltipElement,
     offset: [0, -15],
     positioning: 'bottom-center',
+    stopEvent: false,
+    insertFirst: false,
   });
   map.addOverlay(measureTooltip);
 }