[Feature]: Support for Slack

[r0b0ji]

Use case

As a user of slack, I would like to interact with the ralph-orchestrator through slack. I should be able to:

1. Start a simple task by providing prompt as a slack message or sending prompt as an attachment
2. Check the status
3. ralph-orchestrator should inform me through slack for any user intervention, status of tasks, any failure

Proposed solution

Something similar to ralph-telegram assuming the user has a slack bot listening in socket mode.

Area

CLI

Backend(s) impacted

No response

Alternatives considered

No response

Additional context

No response