Add jupyterhub-idle-culler

Dockerfile

@@ -10,7 +10,7 @@ RUN cd /src \
     && pip wheel -w wheels -e .
 
 FROM quay.io/jupyterhub/jupyterhub:5
-RUN pip install --no-cache-dir dockerspawner
+RUN pip install --no-cache-dir dockerspawner jupyterhub-idle-culler
 RUN apt-get -q update \
     && env DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends podman \
     && rm -fr /var/lib/apt/lists/*