Documented usage of js client lib

docs/jsclientlib/index.rst

@@ -4,6 +4,42 @@
 JavaScript Client Library
 #########################
 
+The JS Client Library provides an interface to all of OctoPrint's API, including the SockJS based socket to send
+push messages from the server to connected clients. It is available as packed web asset file at ``/static/webassets/packed_client.js`` or as individual
+component files at ``/static/js/app/client/<component>.js`` relative to your
+OctoPrint instance's base URL (e.g. ``http://octopi.local/static/webassets/packed_client.js``).
+
+If you are using it from a web page hosted on OctoPrint as a Jinja2 template, you should use one of the following
+methods to embed it instead of manually entering the URL, in order to have OctoPrint take care of setting the
+correct URL prefix:
+
+.. code-block:: html
+
+   <!--
+     full client library or all individual files, depending
+     on the server mode - should be the preferred variant
+   -->
+   {% assets "js_client" %}<script type="text/javascript" src="{{ ASSET_URL }}"></script>{% endassets %}
+
+   <!--
+     full client library
+   -->
+   <script type="text/javascript" src="{{ url_for("static", filename="webassets/packed_client.js") }}"></script>
+
+   <!--
+     individual components
+   -->
+   <script type="text/javascript" src="{{ url_for("static", filename="js/app/client/<component>.js") }}"></script>
+
+Note that all components depend on the ``base`` component to be present, so if you are only including a select
+number of components, make sure to at the very least include that one to be able to utilize the client.
+
+.. seealso::
+
+   `OctoPrint-ForceLogin <https://github.com/OctoPrint/OctoPrint-ForceLogin>`_
+       A plugin that disables anonymous access to the regular OctoPrint UI by implementing a custom UI. Utilizes the
+       client library's :ref:`browser component <sec-jsclientlib-browser>` to login the user.
+
 .. toctree::
    :maxdepth: 3