Revise caption for multi-container example

What's being illustrated here is a volume that has the same lifecycle as
a Pod, so:
- don't use a PersistentVolume as the example
- highlight that the file puller is a sidecar

and give this aspect of the page its own heading.

Author: Tim Bannister

content/en/docs/concepts/workloads/pods/pod-lifecycle.md

@@ -48,17 +48,16 @@ A given Pod (as defined by a UID) is never "rescheduled" to a different node; in
 that Pod can be replaced by a new, near-identical Pod, with even the same name if
 desired, but with a different UID.
 
+### Associated lifetimes
+
 When something is said to have the same lifetime as a Pod, such as a
 {{< glossary_tooltip term_id="volume" text="volume" >}},
 that means that the thing exists as long as that specific Pod (with that exact UID)
 exists. If that Pod is deleted for any reason, and even if an identical replacement
 is created, the related thing (a volume, in this example) is also destroyed and
 created anew.
 
-{{< figure src="/images/docs/pod.svg" title="Pod diagram" class="diagram-medium" >}}
-
-A multi-container Pod that contains a file puller and a
-web server that uses a persistent volume for shared storage between the containers.
+{{< figure src="/images/docs/pod.svg" title="Figure 1." class="diagram-medium" caption="A multi-container Pod that contains a file puller [sidecar](/docs/concepts/workloads/pods/sidecar-containers/) and a web server. The Pod uses an [ephemeral `emptyDir` volume](/docs/concepts/storage/volumes/#emptydir) for shared storage between the containers." >}}
 
 ## Pod phase