Tech Debt: Study creation cleanup

[dogversioning]

Currently, there are two ways a user can create a study:

• By cloning a template from github
• Via the CLI's create command

It may be better to support just one way of doing this - internally we're currently only using the first method, but the second is more in line with the spirit of having all the commands available in one place.

We should consider doing one of the following:

• Remove the CLI create method
• Deprecate the github template repo, and have the CLI be a bit more guided about study creation and create git infrastructure/manifest formatting dynamically (see AWS SAM/vite for examples of good guided CLI flows
• If keeping both, consider adding a task in the PR template to remind to cross-update on changes.

[dogversioning]

So - this is now covered by the Cumulus docsite - we may elect to make this the 'official' way to make a study, in which case we'll deprecate the other creation mechanisms.