Prettier not mandatory

[lorenzogm]

This is an example why prettier shouldn't be required: https://github.com/valtech-ch/ring/runs/2858342339?check_suite_focus=true

I need to install prettier and delay the action more than minute

it would be nice to have a parameter to disable it. Do you accept a PR for it?

Originally posted by @lorenzogm in #32 (comment)