Add subscription hot reload note to pubsub-overview

Signed-off-by: joshvanl <me@joshvanl.dev>

daprdocs/content/en/developing-applications/building-blocks/pubsub/pubsub-overview.md

@@ -84,6 +84,12 @@ Dapr applications can subscribe to published topics via two methods that support
 
 For more information, read [about the subscriptions in Subscription Methods]({{< ref subscription-methods.md >}}).
 
+### Reloading topic subscriptions
+
+To reload topic subscriptions that are defined programmatically or declaratively, the Dapr sidecar needs to be restarted.
+The Dapr sidecar can be made to dynamically reload updated declarative topic subscriptions without restarting by enabling the [`HotReload` feature gate]({{< ref "support-preview-features.md" >}}).
+Hot reloading of topic subscriptions is currently a preview feature.
+
 ### Message routing
 
 Dapr provides [content-based routing](https://www.enterpriseintegrationpatterns.com/ContentBasedRouter.html) pattern. [Pub/sub routing]({{< ref howto-route-messages.md >}}) is an implementation of this pattern that allows developers to use expressions to route [CloudEvents](https://cloudevents.io) based on their contents to different URIs/paths and event handlers in your application. If no route matches, an optional default route is used. This is useful as your applications expands to support multiple event versions or special cases.