Suggest use of `url` tag to locate i18n javascript view

[Joost Cassee]

Please change the documentation for the i18n javascript_catalog view to use the url tag, to match best practices:

<script type="text/javascript" src="/path/to/jsi18n/"></script>

becomes

<script type="text/javascript" src="{% url django.views.i18n.javascript_catalog %}"></script>

[Russell Keith-Magee]

(In [11237]) Fixed #11364 -- Modified the jsi18n example to use the {% url %} tag rather than a placeholder. Thanks to jcassee for the suggestion.