add Julia in Jupyter doc

Author: omlins

docs/services/jupyterlab.md

@@ -45,7 +45,7 @@ A kernel can be created from an active Python virtual environment with the follo
 python -m ipykernel install --user --name="<kernel-name>" --display-name="<kernel-name>"
 ```
 
-## Using uenvs in JupyterLab
+## Using uenvs in JupyterLab for Python
 
 In the JupyterHub Spawner Options form mentioned above, it's possible to pass an uenv and a view.
 The uenv will be mounted at `/user-environment`, and the specified view will be activated.
@@ -65,6 +65,27 @@ Then with that virtual environment activated, you can run the command to create
     If the uenv is not present in the local repository, it will be automatically fetched.
     As a result, JupyterLab may take slightly longer than usual to start.
 
+
+## Using Julia in JupyterHub
+
+Each time you start a JupyterHub server, you need to do the following in the JupyterHub Spawner Options form mentioned above:
+!!! important "pass a [`julia`][ref-uenv-julia] uenv and the view `jupyter`."
+
+At first time use of Julia within Jupyter, IJulia and one or more Julia kernel needs to be installed. Type the following command in a shell within JupyterHub to install IJulia, the default Julia kernel and, on systems whith Nvidia GPUs, a Julia kernel running under Nvidia Nsight Systems:
+```console
+install_ijulia
+```
+
+You can install additional custom Julia kernels by typing the following in a shell:
+```console
+julia
+using IJulia
+installkernel(<args>) # type `? installkernel` to learn about valid `<args>`
+```
+
+!!! warning "First time use of Julia"
+    If you are using Julia for the first time at all, executing `install_ijulia` will automatically first trigger the installation of `juliaup` and the latest `julia` version (it is also triggered if you execute `juliaup` or `julia`).
+
 ## Ending your interactive session and logging out
 
 The Jupyter servers can be shut down through the Hub. To end a JupyterLab session, please select `Control Panel` under the `File` menu and then `Stop My Server`. By contrast, clicking `Logout` will log you out of the server, but the server will continue to run until the Slurm job reaches its maximum wall time.