Remove extremely out-of-date documentation. The XKCD/APOD/mp4 tutorials are

much better for this now.

docs/source/developer/adding_content.rst

@@ -1,38 +0,0 @@
-Adding Content
---------------
-
-As an example: Add a leaflet viewer plugin for geoJSON files.
-
--  Go to npm: search for
-   `leaflet <https://www.npmjs.com/package/leaflet>`__ (success!).
-
--  Go to ``jupyterlab`` top level source directory:
-   ``jlpm add leaflet``. This adds the file to the ``dependencies`` in
-   ``package.json``.
-
--  Next we see if there is a typing declaration for leaflet:
-   ``jlpm add --dev @types/leaflet``. Success!
-
--  If there are no typings, we must create our own. An example typings
-   file that exports functions is
-   `codemirror <https://github.com/jupyterlab/jupyterlab/blob/master/packages/codemirror/typings/codemirror/codemirror.d.ts>`__.
-
--  Add a reference to the new library in ``src/typings.d.ts``.
-
--  Create a folder in ``src`` for the plugin.
-
--  Add ``index.ts`` and ``plugin.ts`` files.
-
--  If creating CSS, import them in ``src/default-themes/index.css``.
-
--  The ``index.ts`` file should have the core logic for the plugin. In
-   this case, it should create a widget and widget factory for rendering
-   geojson files (see :ref:`documents`).
-
--  The ``plugin.ts`` file should create the extension and add the
-   content to the application. In this case registering the widget
-   factory using the document registry.
-
--  Run ``jlpm run build`` from ``jupyterlab/jupyterlab``
-
--  Run ``jupyter lab`` and verify changes.

docs/source/index.rst

@@ -56,7 +56,6 @@ JupyterLab is the next-generation web-based user interface for Project Jupyter.
    developer/css
    developer/documentation
    developer/virtualdom
-   developer/adding_content
    developer/examples
    developer/ui_helpers
    developer/terminology