Add PullRequestReviewEvent documentation

Author: lowlighter

content/developers/webhooks-and-events/github-event-types.md

@@ -181,6 +181,19 @@ This event returns an empty `payload` object.
 {% data reusables.webhooks.pull_request_event_api_properties %}
 {% data reusables.webhooks.pull_request_properties %}
 
+### PullRequestReviewEvent
+
+{% data reusables.webhooks.pull_request_review_short_desc %}
+{% data reusables.webhooks.events_api_payload %}
+
+#### Event `payload` object
+
+Key | Type | Description
+----|------|-------------
+`action` | `string` | The action that was performed. Can be `created`.
+`pull_request` | `object` | The pull request the review pertains to.
+`review` | `object` |	The review that was affected.
+
 ### PullRequestReviewCommentEvent
 
 {% data reusables.webhooks.pull_request_review_comment_short_desc %}
@@ -198,6 +211,8 @@ This event returns an empty `payload` object.
 
 {% data reusables.webhooks.events_api_payload %}
 
+#### Event `payload` object
+
 Key | Type | Description
 ----|------|-------------
 `push_id` | `integer` | Unique identifier for the push.