docs: add user docs for custom volumes/volume mounts

Author: Bobbins228

docs/sphinx/user-docs/cluster-configuration.rst

@@ -26,6 +26,8 @@ requirements for creating the Ray Cluster.
        worker_memory_limits=2, # Default 2
        # image="", # Optional Field
        labels={"exampleLabel": "example", "secondLabel": "example"},
+       volumes=[], # See Custom Volumes/Volume Mounts
+       volume_mounts=[], # See Custom Volumes/Volume Mounts
    ))
 
 .. note::
@@ -48,6 +50,53 @@ apply additional labels to the RayCluster resource.
 After creating their ``cluster``, a user can call ``cluster.up()`` and
 ``cluster.down()`` to respectively create or remove the Ray Cluster.
 
+Custom Volumes/Volume Mounts
+----------------------------
+| To add custom Volumes and Volume Mounts to your Ray Cluster you need to create two lists ``volumes`` and ``volume_mounts``. The lists consist of ``V1Volume`` and ``V1VolumeMount`` objects respectively.
+| Populating these parameters will create Volumes and Volume Mounts for the head and each worker pod.
+
+.. code:: python
+
+  from kubernetes.client import V1Volume, V1VolumeMount, V1EmptyDirVolumeSource, V1ConfigMapVolumeSource, V1KeyToPath, V1SecretVolumeSource
+  # In this example we are using the Config Map, EmptyDir and Secret Volume types
+  volume_mounts_list = [
+      V1VolumeMount(
+          mount_path="/home/ray/test1",
+          name = "test"
+      ),
+      V1VolumeMount(
+          mount_path = "/home/ray/test2",
+          name = "test2",
+      ),
+      V1VolumeMount(
+          mount_path = "/home/ray/test3",
+          name = "test3",
+      )
+  ]
+
+  volumes_list = [
+      V1Volume(
+          name="test",
+          empty_dir=V1EmptyDirVolumeSource(size_limit="2Gi"),
+      ),
+      V1Volume(
+          name="test2",
+          config_map=V1ConfigMapVolumeSource(
+              name="test-config-map",
+              items=[V1KeyToPath(key="test", path="data.txt")]
+          )
+      ),
+      V1Volume(
+          name="test3",
+          secret=V1SecretVolumeSource(
+              secret_name="test-secret"
+          )
+      )
+  ]
+
+| For more information on creating Volumes and Volume Mounts with Python check out the Python Kubernetes docs (`Volumes <https://github.com/kubernetes-client/python/blob/master/kubernetes/docs/V1Volume.md>`__, `Volume Mounts <https://github.com/kubernetes-client/python/blob/master/kubernetes/docs/V1VolumeMount.md>`__).
+| You can also find further information on Volumes and Volume Mounts by visiting the Kubernetes `documentation <https://kubernetes.io/docs/concepts/storage/volumes/>`__.
+
 Deprecating Parameters
 ----------------------