Add comma

Author: dippynark

content/en/docs/concepts/containers/container-lifecycle-hooks.md

@@ -40,7 +40,7 @@ This hook is called immediately before a container is terminated due to an API r
 event such as a liveness/startup probe failure, preemption, resource contention and others. A call
 to the `PreStop` hook fails if the container is already in a terminated or completed state and the
 hook must complete before the TERM signal to stop the container can be sent. The Pod's termination
-grace period countdown begins before the `PreStop` hook is executed so regardless of the outcome of
+grace period countdown begins before the `PreStop` hook is executed, so regardless of the outcome of
 the handler, the container will eventually terminate within the Pod's termination grace period. No
 parameters are passed to the handler.