Add keep_linebreaks parameter to text loader

[lhoestq]

As asked in #870 and huggingface/transformers#10269 there should be a parameter to keep the linebreaks when loading a text dataset.
cc @sgugger @jncasey

[sgugger]

Just so I understand how it can be used in practice, do you have an example showing how to load a text dataset with this option?

[lhoestq]

Sure ! Here is an example:

from datasets import load_dataset

load_dataset("text", keep_linebreaks=True, data_files=...)

I'll update the documentation to explain this

[sgugger]

Perfect!