feat: mount themes & requirements in dev job containers

These bind-mounts:

* ../build/openedx/themes:/openedx/themes
* ../build/openedx/requirements:/openedx/requirements

existed in the dev lms and cms containers, but they did
not exist in the lms-job and cms-job containers.

This means that themes and requirements that were *built into the
image* would exist in the job containers, but live updates to the
themes and requirements would not apply.

To resolve this, we set ``volumes:`` on the lms-job and cms-job
services so that they match the volumes for the normal lms and
cms services.

tutor/templates/dev/docker-compose.jobs.yml

@@ -9,6 +9,15 @@ x-openedx-job-service:
     args:
       # Note that we never build the openedx-dev image with root user ID, as it would simply fail.
       APP_USER_ID: "{{ HOST_USER_ID or 1000 }}"
+  volumes:
+    # Settings & config
+    - ../apps/openedx/settings/lms:/openedx/edx-platform/lms/envs/tutor:ro
+    - ../apps/openedx/settings/cms:/openedx/edx-platform/cms/envs/tutor:ro
+    - ../apps/openedx/config:/openedx/config:ro
+    # theme files
+    - ../build/openedx/themes:/openedx/themes
+    # editable requirements
+    - ../build/openedx/requirements:/openedx/requirements
 
 services: