Add dummy dart:html library for documentation.

lib/html/doc/interface/SVGNumberList.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// WARNING: Do not edit - generated code.
+
+/// @domName SVGNumberList
+interface SVGNumberList {
+
+  /** @domName SVGNumberList.numberOfItems */
+  final int numberOfItems;
+
+  /** @domName SVGNumberList.appendItem */
+  SVGNumber appendItem(SVGNumber item);
+
+  /** @domName SVGNumberList.clear */
+  void clear();
+
+  /** @domName SVGNumberList.getItem */
+  SVGNumber getItem(int index);
+
+  /** @domName SVGNumberList.initialize */
+  SVGNumber initialize(SVGNumber item);
+
+  /** @domName SVGNumberList.insertItemBefore */
+  SVGNumber insertItemBefore(SVGNumber item, int index);
+
+  /** @domName SVGNumberList.removeItem */
+  SVGNumber removeItem(int index);
+
+  /** @domName SVGNumberList.replaceItem */
+  SVGNumber replaceItem(SVGNumber item, int index);
+}