Configurable path to lefthook to run during git hook

[technicalpickles]

⚡ Summary

This adds LEFTHOOK_PATH to the .git/hook templates. It's used first before

This is something that would have been helpful while working on #588 and I was testing against a locally built

While I was here, I added set -x when LEFTHOOK_VERBOSE is on. This is another thing that would have been useful, and I also used it to help validate LEFTHOOK_PATH working 😁 Let me know if I should split it out separately.

☑️ Checklist

• Check locally
• Add tests
• Add documentation

[mrexox]

Thank you!