feat(bundles): allow parent bundles to scaffold bundle file in tildepot repo

[echocrow]

when creating a new bundle based on a parent bundle, that parent bundle could control how to scaffold out the new files bundle in the user tildepot repo

that bootstrapped file could be generated dynamically, so bundles can implement e.g. prompts for a user-friendly, self-guided approach to leveraging customizable bundles

this would build on top of #4 & #6