Make the URL for the Slack "Open view" action configurable.

[jkeyes]

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

I have deployed komiser on our network, but when I press the "Open view" action in the Slack alert it refers to http://localhost instead of the server where it is deployed.

Describe the solution you'd like
When I press "Open view" I would like the instance of komiser that sent the alert to open in the browser.

[github-actions]

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[jkeyes]

FYI I'm preparing a PR for this issue.