https://linear.app/unleash/issue/2-1235/docs-slack-app-integration-documentation
This adds a new reference doc for the new Unleash Slack App integration
and marks the previous Slack integration as deprecated.
As a side-effect this PR also fixes an issue where we wouldn't be able
to delete tags with special characters.
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Co-authored-by: David Leek <david@getunleash.io>
Co-authored-by: Thomas Heartman <thomas@getunleash.ai>
