docs(error/$injector/modulerr): add info about not monkey-patching ng

Closes #7709
Closes #9692

docs/content/error/$injector/modulerr.ngdoc

@@ -6,6 +6,22 @@
 This error occurs when a module fails to load due to some exception. The error
 message above should provide additional context.
 
+### Using `ngRoute`
+
 In AngularJS `1.2.0` and later, `ngRoute` has been moved to its own module.
 If you are getting this error after upgrading to `1.2.x` or later, be sure that you've
 installed {@link ngRoute `ngRoute`}.
+
+### Monkey-patching Angular's `ng` module
+
+This error can also occur if you have tried to add your own components to the `ng` module.
+This has never been supported and from `1.3.0` it will actually trigger this error.
+For instance the following code could trigger this error.
+
+```js
+angular.module('ng').filter('tel', function (){});
+```
+
+Instead create your own module and add it as a dependency to your application's top-level module.
+See [#9692](https://github.com/angular/angular.js/issues/9692) and
+[#7709](https://github.com/angular/angular.js/issues/7709) for more information