Add link to slack channel in the incidents list (or a link to set/create a slack channel if one not set)

[sploschee]

Is your feature request related to a problem? Please describe.
When reviewing live incidents in Backstage, have a number of clicks between me and the active Slack channel can be friction that I could do without.

Describe the solution you'd like
It would be helpful to be able to view, and navigate to, the Slack channel associated with an incident from within Backstage.
If a Slack channel has not been set, the ability to set or create one from within the plugin would be helpful.