Added hotkey support to viewerbase

Packages/viewerbase/lib/switchToImageByIndex.js

@@ -0,0 +1,13 @@
+/**
+ * This function switches to an image given an element and the index of the image in the current stack
+ * Note: Negative indexing is supported:
+ * 
+ *      e.g. switchToImageByIndex(element, -1) to switch to the last image of the stack
+ * 
+ * @param element
+ * @param {number} [newImageIdIndex] The image index in the stack to switch to.
+ */
+switchToImageByIndex = function(newImageIdIndex) {
+    var element = getActiveViewportElement();
+    cornerstoneTools.scrollToIndex(element, newImageIdIndex);
+};