Post to internal slack if nightly tests fail

[praateekmahajan]

Is your feature request related to a problem? Please describe.
If nightly scheduled tests fail then we would like to be notified on slack.
Describe the solution you'd like
Code as follows could work however we'd have to figure out the slack auth tokens

      - name: Notify on failure
        if: failure() && github.event_name == 'schedule'
        uses: slackapi/slack-github-action@v1
        with:
          channel-id: 'xyz'
          slack-message: "Nightly GPU tests failed! Check: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}"
        env:
          SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }} # add secret somewhere

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.