Update Actors healhcheck endpoint (#460)

reference/api/actors_api.md

@@ -666,7 +666,7 @@ curl -X POST http://localhost:3000/actors/stormtrooper/50/method/remind/checkReb
 
 ### Invoke timer
 
-Invokes a timer for an acto rwith the specified timerName
+Invokes a timer for an actor rwith the specified timerName
 
 #### HTTP Request
 
@@ -700,6 +700,39 @@ curl -X POST http://localhost:3000/actors/stormtrooper/50/method/timer/checkRebe
   -H "Content-Type: application/json"
 ```
 
+### Health check
+
+Probes the application for a response to signal to Dapr that the app is healthy and running.
+Any other response status code other than `200` will be considered as an unhealthy response.
+
+A response body is not required.
+
+#### HTTP Request
+
+```http
+GET http://localhost:<appPort>/healthz
+```
+
+#### HTTP Response Codes
+
+Code | Description
+---- | -----------
+200  | App is healthy
+
+#### URL Parameters
+
+Parameter | Description
+--------- | -----------
+appPort | The application port.
+
+#### Examples
+
+Example of getting a health check response from the app:
+
+```shell
+curl -X GET http://localhost:3000/healthz \
+```
+
 ## Querying actor state externally
 
 In order to enable visibility into the state of an actor and allow for complex scenarios such as state aggregation, Dapr saves actor state in external state stores such as databases. As such, it is possible to query for an actor state externally by composing the correct key or query.