Add tooltip to google 3d tiles example

This demonstrates the working picking on layers draped over terrain
cover.

Author: flostellbrink

examples/website/google-3d-tiles/app.jsx

@@ -32,6 +32,17 @@ const INITIAL_VIEW_STATE = {
 const BUILDING_DATA =
   'https://raw.githubusercontent.com/visgl/deck.gl-data/master/examples/google-3d-tiles/buildings.geojson';
 
+function getTooltip({object}) {
+  return (
+    object && {
+      html: `\
+    <div><b>Distance to nearest tree</b></div>
+    <div>${object.properties.distance_to_nearest_tree} / parcel</div>
+    `
+    }
+  );
+}
+
 export default function App({data = TILESET_URL, distance = 0, opacity = 0.2}) {
   const [credits, setCredits] = useState('');
 
@@ -64,7 +75,8 @@ export default function App({data = TILESET_URL, distance = 0, opacity = 0.2}) {
       getFillColor: ({properties}) => colorScale(properties.distance_to_nearest_tree),
       opacity,
       getFilterValue: f => f.properties.distance_to_nearest_tree,
-      filterRange: [distance, 500]
+      filterRange: [distance, 500],
+      pickable: true
     })
   ];
 
@@ -75,6 +87,7 @@ export default function App({data = TILESET_URL, distance = 0, opacity = 0.2}) {
         initialViewState={INITIAL_VIEW_STATE}
         controller={{touchRotate: true, inertia: 250}}
         layers={layers}
+        getTooltip={getTooltip}
       />
       <div
         style={{position: 'absolute', left: '8px', bottom: '4px', color: 'white', fontSize: '10px'}}