docs(cli): Document send-event format (#10995)

Link to the [Event Payloads](https://develop.sentry.dev/sdk/event-payloads/) page from the `send-event` command page, so that users know what format their event should follow.

Closes #9538

docs/cli/send-event.mdx

@@ -70,7 +70,7 @@ sentry-cli send-event -m "a failure" -t task:create-user
 
 ## Stored Events
 
-As of version `1.71`, the `send-event` command can accept an optional argument that specifies a path to the stored JSON representation of an event. When used, it will load the file, validate the event and send it to Sentry.
+As of version `1.71`, the `send-event` command can accept an optional argument that specifies a path to the stored JSON representation of an [event payload](https://develop.sentry.dev/sdk/event-payloads/). When used, it will load the file, validate the event and send it to Sentry.
 
 ```bash
 sentry-cli send-event ./events/20211029150006.json