update testplan with docker instructions for mac / linux (#12940)

Co-authored-by: Ian Huff <[email protected]>

Author: IanMatthewHuff

.github/test_plan.md

@@ -576,23 +576,29 @@ def test_failure():
     1. Run a cell on the host
     1. Verify the editor opens on the guest and the cell is run there too
 -   [ ] Jupyter Hub support
-    1. Install Docker Desktop onto a machine
-    1. Create a folder with a file 'Dockerfile' in it.
-    1. Mark the file to look like so:
-
-    ``` 
-    ARG BASE_CONTAINER=jupyterhub/jupyterhub
-    FROM $BASE_CONTAINER
-
-    USER root
-
-    USER $NB_UID
-    ```
-
-    1. From a command prompt (in the same folder as the Dockerfile), run ```docker build -t jupyterhubcontainer:1.0 .```
-    1. Run ```docker container create --name jupyterhub jupyterhubcontainer:1.0 jupyterhub```
-    1. From the docker desktop app, start the jupyterhub container. 
-    1. From the docker desktop app, run the CLI 
+    1. Windows install instructions
+        1. Install Docker Desktop onto a machine
+        1. Create a folder with a file 'Dockerfile' in it.
+        1. Mark the file to look like so:
+
+        ``` 
+        ARG BASE_CONTAINER=jupyterhub/jupyterhub
+        FROM $BASE_CONTAINER
+
+        USER root
+
+        USER $NB_UID
+        ```
+
+        1. From a command prompt (in the same folder as the Dockerfile), run ```docker build -t jupyterhubcontainer:1.0 .```
+        1. Run ```docker container create --name jupyterhub jupyterhubcontainer:1.0 jupyterhub```
+        1. From the docker desktop app, start the jupyterhub container. 
+        1. From the docker desktop app, run the CLI 
+    1. OR Mac / Linux install instructions
+        1. Install docker
+        1. From the terminal ```docker run -p 8000:8000 -d --name jupyterhub jupyterhub/jupyterhub jupyterhub```
+        1. Open a terminal in the docker container with ```docker exec -it jupyterhub bash```
+        1. From that terminal run ```python3 -m pip install notebook```
     1. From the new command prompt, run ```adduser testuser```
     1. Follow the series of prompts to add a password for this user
     1. Open VS code