Add hello world workflow to help diagnose GitHub token issues

[b9r5]

Description

This PR adds a hello world workflow in GitHub, and a script to run the workflow. I am hoping that this will help diagnose problems that new contributors have with getting set up.

Unfortunately, I don't think it's possible to test the script until this PR is merged, because the workflow isn't showing up for me when I run the script:

$ python3 src/discord-cluster-manager/run_hello_world_workflow.py
2024-12-28 10:39:37 - utils - INFO - Found workflow: AMD PyTorch Job
2024-12-28 10:39:37 - utils - INFO - Found workflow: Lint
2024-12-28 10:39:37 - utils - INFO - Found workflow: NVIDIA PyTorch/CUDA Job
2024-12-28 10:39:37 - utils - INFO - Found workflow: .github/workflows/pr_workflow.yml
2024-12-28 10:39:37 - utils - INFO - Found workflow: Training Workflow
2024-12-28 10:39:37 - utils - ERROR - GitHub API error: 404 - Not Found

Checklist

Before submitting this PR, ensure the following steps have been completed:

• Run the slash command /verifyruns on your own server.
  • Run the cluster bot on your server:

    python discord-bot.py

  • Start training runs with the slash command /verifyruns.
  • Verify that the bot eventually responds with:

    ✅ All runs completed successfully!
    

    (It may take a few minutes for all runs to finish. In particular, the GitHub
    runs may take a little longer. The Modal run is typically quick.)
    For more information on running a cluster bot on your own server, see
    README.md.