challenge(formatter): add lineEnding option

[SuperchupuDev]

Summary

The Prettier challenge requires us to add all Prettier options relevant when formatting JS

This PR adds a lineEnding option, with the following values:

• lf
• crlf
• cr

Test Plan

Added one new test, line-ending.js

[LivSarah]

Is there a specific reason why the auto option was not included ? (:
(ref: Prettier options)

I'm currently working on a project where we use Biome, and we're having problems with (what I assume has to be) the line-endings. We faced a similar problem when using prettier/eslint in a different project, and the best solution turned out to use the auto option for line endings. 🤔

Edit:
I saw that the original issue also specifically mentioned "auto".

[ematipico]

Some of us had reservations about options that aren't predictable, such as this auto and quoteProps="consistent". These can cause different outputs depending on the machines of the users.

In particular for line ending, some of us thought that users should use git to solve line endings resolutions among files.

[LivSarah]

As I usually prefere to keep things like this predictable myself, I can understand to some degree. I just also aknowledge the need for "grey areas" once in a while I think. 😅

So this means it was a conscious decision to leave out "auto" when adding the lineEnding option, and that there is no point in creating an issue for it? 😇

[ematipico]

You could create a GitHub discussion and build a case for the option! Why you need it, explain your use case, etc