Slack Plugin Details Page - Notification Type is not supported

## Description
clicking the title `https:/hostname.domain.com/alerts/notifications/{notificationid}` gives an error `Slack Notification Type` not supported.

## Steps To Reproduce
1.create a slack notification.
2.click the `title` of the slack notification.
3.details page is rendering, that Slack Notification is not supported.


## Possible Solution - add details component like below :
```eventNotificationTypes: [
{
type: 'slack-notification-v1',
displayName: 'Slack Notification',
formComponent: SlackNotificationForm,
summaryComponent: SlackNotificationSummary,
detailsComponent:SlackDetailsComponent,
defaultConfig: SlackNotificationForm.defaultConfig,
},
]
```

## Environment

- Graylog Version:4.0
- Elasticsearch Version:7.x
- MongoDB Version:
- Browser Version: