feat: reload and reconnect the app process after updating files

[zimeg]

Type of change

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

Summary

This PR automatically reloads the process and reconnects the Socket Mode connection after a file is changed. All in hopes of improving the development experience.

Reviewers

$ slack create asdf -t slack-samples/bolt-js-custom-function-template -b zimeg/feat-start-reload
$ cd asdf
$ slack run           # Run the app in some separate window
$ vim app.js          # Make a change to the app and watch a reload
$ vim manifest.json   # Update the manifest and notice the app is reinstalled
$ slack delete
$ cd .. && rm -rf asdf

Notes

• https://github.com/remy/nodemon

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]

@seratch appreciate the approval for this! From some discussion it sounds like documenting this as a possibility is the approach we're going with for now. I like the idea from @WilliamBergamin in slack-samples/bolt-python-custom-functions#19 of including this in hooks, but see how that comes with maintenance burden...

Hoping to have this documented somewhere sometime soon, but will close this PR for the time being.