merge new into master

node_modules/use-callback-ref/dist/es2015/createRef.js

@@ -0,0 +1,23 @@
+/**
+ * creates a Ref object with on change callback
+ * @param callback
+ * @returns {RefObject}
+ *
+ * @see {@link useCallbackRef}
+ * @see https://reactjs.org/docs/refs-and-the-dom.html#creating-refs
+ */
+export function createCallbackRef(callback) {
+    var current = null;
+    return {
+        get current() {
+            return current;
+        },
+        set current(value) {
+            var last = current;
+            if (last !== value) {
+                current = value;
+                callback(value, last);
+            }
+        },
+    };
+}