Add dragzoom example, configured with canvas renderer

examples/dragzoom.js

@@ -0,0 +1,24 @@
+goog.require('ol.Map');
+goog.require('ol.RendererHint');
+goog.require('ol.View2D');
+goog.require('ol.interaction.DragZoom');
+goog.require('ol.layer.Tile');
+goog.require('ol.source.OSM');
+
+
+var map = new ol.Map({
+  layers: [
+    new ol.layer.Tile({
+      source: new ol.source.OSM()
+    })
+  ],
+  renderer: ol.RendererHint.CANVAS,
+  target: 'map',
+  view: new ol.View2D({
+    center: [0, 0],
+    zoom: 2
+  })
+});
+
+var dragzoom = new ol.interaction.DragZoom();
+map.addInteraction(dragzoom);