Backport PR jupyterlab#457: Add step to create a GPT4All cache folder…

… to the docs (jupyterlab#458)

Co-authored-by: Andrii Ieroshenko <[email protected]>

docs/source/users/index.md

@@ -378,6 +378,12 @@ Note that each model comes with its own license, and that users are themselves
 responsible for verifying that their usage complies with the license. You can
 find licensing details on the [GPT4All official site](https://gpt4all.io/index.html).
 
+First, create a folder to store the model files.
+
+```
+mkdir ~/.cache/gpt4all
+```
+
 For each model you use, you will have to run the command
 
 ```