Added port forwarding for docker

gt-workbench.md

@@ -62,9 +62,17 @@ it does not have to be like this, as you can have many containers based on the
 same image.
 
 ```bash
-docker create --platform linux/amd64 -i -t -v .:/work --name gt-workbench gt-workbench
+docker create --platform linux/amd64 -p 3000:3000 -i -t -v .:/work --name gt-workbench gt-workbench
 ```
 
+:::{warning} Port forwarding with Docker
+Port forwarding is required so that myst running inside docker can be accessed from your browser.
+The port can be specified via
+```bash
+-p HOSTPORT:CONTAINERPORT
+```
+:::
+
 The container is in principle isolated from the host OS, but we usually want to
 exchange files with it; so the above command also binds the current working
 directory in the host OS with a directory ``/work`` inside the container.