Feature request: set color automatically based on build status

[vitalykarasik]

It'll be nice to see this plugin to set Slack color automatically based on the job status, i.e.
success => green
failed => red
warning => orange

[vitalykarasik]

Suggested into Readme method for "Reporting Success or Failure" isn't elegant, I'm using the following.
But there are more possible statuses...

with: status: ${{ job.status }} color: ${{ job.status == 'success' && 'good' || 'danger' }}