Update package and user included files to .md

docs/install/add-packages.md

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+The **User Environment** is a conda environment that is shared by all users
+in the JupyterHub. Libraries installed in this environment are immediately
+available to all users. Admin users can install packages in this environment
+with `sudo -E`.
+
+1. Log in as an admin user and open a Terminal in your Jupyter Notebook.
+
+   ```{image} ../images/notebook/new-terminal-button.png
+   :alt: New Terminal button under New menu
+   ```
+
+2. Install [gdal](https://anaconda.org/conda-forge/gdal) from [conda-forge](https://conda-forge.org/).
+
+   ```bash
+   sudo -E conda install -c conda-forge gdal
+   ```
+
+   The `sudo -E` is very important!
+
+3. Install [there](https://pypi.org/project/there) with `pip`
+
+   ```bash
+   sudo -E pip install there
+   ```
+
+The packages `gdal` and `there` are now available to all users in JupyterHub.
+If a user already had a python notebook running, they have to restart their notebook's
+kernel to make the new libraries available.
+
+See [](#howto/user-env/user-environment) for more information.