[eslint-config] Set prettier as optional or remove it

[smujaddid]

I suggest to remove prettier from eslint-config or set it as optional.
By making it optional, if the user installed prettier as a dependency then the eslint-prettier-plugin will be loaded and used, otherwise don't load it at all.

Personally, I abandoned prettier usage as I prefer to use both ESLint Stylistic and Stylelint for formatting code and css files.
I know both eslint stylistic and stylelint are not the same as prettier, especially for HTML formatting. But, making it optional would be helpful for some developers who don't want to use prettier in any form.

I can always create my own config to use for my Adonis-based project, but if I can use the provided plugin by Adonis, then I prefer that instead.

This is just an opinion and a small request. I don't mean to disrespect anyone's preference. Everyone has their own setup and preference. That's it.

Thank you.