Feature request: allow config prettier from outside

First of all thank you for this package, it is really useful for me!

Currently there is no way to config prettier from some ui, and I needed to change the installed package to adjust the wanted styles.

It would be nice to allow pass the entire prettier config from out site.

I will review `alfy` to check if it is support it, if so, I will create a PR :]

Review the requested external Prettier configuration and investigate the referenced alfy support. Define how the entire configuration should be passed from outside the installed package; the work is done when users can adjust styles without modifying the installed package and the behavior is covered by appropriate project checks.

Written by the indexing model from the issue text.