Being able to pass a local template to `rnv new` non-interactively

[locksten]

Is your feature request related to a problem? Please describe. To automate caching of rnv templates, we need to be able to run rnv new with a path to a local template non-interactively. It seems like currently it's only possible to do that interactively (link).

Describe the solution you'd like A new option like rnv new --localTemplate /path/to/template, or rnv recognizing when rnv new --project-template /path/to/template is a local path.