XFA - Add a parser for XFA files

- the parser is base on a class extending XMLParserBase
 - it handle xml namespaces:
   * each namespace is assocated with a builder
   * builder builds nodes belonging to the namespace
   * when a node is inserted in the parent namespace compatibility is checked (if required)
 - to avoid name collision between xml names and object properties, use Symbol.

src/core/xfa/setup.js

@@ -0,0 +1,24 @@
+/* Copyright 2021 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { ConfigNamespace } from "./config.js";
+import { XdpNamespace } from "./xdp.js";
+
+const NamespaceSetUp = {
+  config: ConfigNamespace,
+  xdp: XdpNamespace,
+};
+
+export { NamespaceSetUp };