feat: include a placeholder deploy hook to avoid missing hook errors

[zimeg]

Type of change

• [ ] New sample
• [x] New feature
• [ ] Bug fix
• [ ] Documentation

Summary

This PR includes a placeholder value for the deploy hook to avoid errors when attempting the deploy command for this app.

Super open to discussion on better wording and values or if this is something to include!

Preview

Before


After

Requirements

• [x] I’ve checked my submission against the Samples Checklist to ensure it complies with all standards
• [x] I have ensured the changes I am contributing align with existing patterns and have tested and linted my code
• [x] I've read and agree to the Code of Conduct

[zimeg]

@WilliamBergamin appreciate the review! I plan to merge this soon, but might use some scripts to handle this across all bolt-js-* and bolt-py-* apps with a slack.json to avoid repeating this PR too much!

[zimeg]

🗒️ Closing this since slack.json isn't being recommended in the README.md at the moment, but hoping to revisit this at a soonish point!