ref(issue-alert): add test notifications and preview (#5959)

* ref(issue-alert): add test notifications and preview

* Update src/docs/product/alerts/create-alerts/issue-alert-config.mdx

Co-authored-by: Isabel <[email protected]>

* a little more info on what previews are not supported

* list non-previewable rules

* Update src/docs/product/alerts/create-alerts/issue-alert-config.mdx

Co-authored-by: Isabel <[email protected]>

* Update src/docs/product/alerts/create-alerts/issue-alert-config.mdx

Co-authored-by: Isabel <[email protected]>

* Update src/docs/product/alerts/create-alerts/issue-alert-config.mdx

Co-authored-by: Isabel <[email protected]>

Co-authored-by: Isabel <[email protected]>

Author: Zandew

src/docs/product/alerts/create-alerts/issue-alert-config.mdx

@@ -100,6 +100,10 @@ If an issue owner is not configured or not found, either the notification won’
 
 Teams can configure a Slack channel to receive alert notifications. This can be done by typing `/sentry link team` in the desired Slack channel. To view a team's associated Slack channel in [sentry.io](https://sentry.io), navigate to **Settings > Teams > [Team] > Notifications**.
 
+### Notification Tests
+
+Notification tests allow you to test if your integrations are working properly. Sending a test notification creates a dummy event and sends a notification to all of the selected integrations.
+
 ## Action Interval (Rate Limit)
 
 The action interval, or rate limit, controls how often the alert rule can be triggered for a particular issue. If alert conditions match an issue, Sentry executes the actions only if they haven't already been executed for that issue within the rate limit period. For example, if an issue meets alert conditions multiple times in a one-minute period, but your frequency threshold is one minute, you’ll only be alerted once.
@@ -110,6 +114,17 @@ The available intervals are:
 - Hours: 3, 12, 24
 - Days: 7, 30
 
+## Alert Preview
+
+The preview displays a list of issues that would have triggered the alert and the last time they would have triggered it.
+
+Rules with any of following can't be previewed:
+- The issue is assigned to {no one/a team/a member}.
+- The event is from the latest release.
+- An issue affects more than [{X} percent of sessions in {time}](#percent-based-alerts)
+- No ["When" conditions](#when-conditions-triggers)
+- Both [issue frequency](#change-alerts) conditions and [event filters](#if-conditions-filters) (filters that start with "The event")
+
 ## Alert Name
 
 Give your alert a descriptive name, such as the team affected and the topic of the alert. For example, "Frontend Latency", "Backend Failure Rate", or "Billing Apdex".