Tag a Slack user group on release notifications

[cseas]

Is your feature request related to a problem? Please describe.

We are using the GitHub integration to subscribe to releases notifications for our repo. But there's no way to automatically tag a Slack user group on the notification so we need to do it manually each time.

Describe the solution you'd like

It would be great if the subscription notifications could be customised in general with a text we want to be added to each notification. In this case, we want to tag a specific Slack user group with each release notification.

Describe alternatives you've considered

Custom Slack notification workflow based on the released github event.

Additional context
N/A