edit source url in build time

.docfx/template/ManagedReference.extension.js

@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+/**
+ * This method will be called at the start of exports.transform in ManagedReference.html.primary.js
+ */
+exports.preTransform = function (model) {
+    return model;
+}
+
+/**
+ * This method will be called at the end of exports.transform in ManagedReference.html.primary.js
+ */
+exports.postTransform = function (model) {
+
+    model.sourceurl += 'xxx';
+
+    return model;
+}