[Feature Request] Add optional parameter in text loading script to preserve linebreaks
I'm working on a project about rhyming verse using phonetic poetry and song lyrics, and line breaks are a vital part of the data. 

I recently switched over to use the datasets library when my various corpora grew larger than my computer's memory. And so far, it is SO great. 

But the first time I processed all of my data into a dataset, I hadn't realized the text loader script was processing the source files line-by-line and stripping off the newlines. 

Once I caught the issue, I made my own data loader by modifying one line in the default text loader (changing `batch = batch.splitlines()` to `batch = batch.splitlines(True)` inside `_generate_tables`). And so I'm all set as far as my project is concerned.

But if my use case is more general, it seems like it'd be pretty trivial to add a kwarg to the default text loader called keeplinebreaks or something, which would default to False and get passed to `splitlines()`. 
Hi ! Thanks for your message.
Indeed it's a free feature we can add and that can be useful.
If you want to contribute, feel free to open a PR to add it to the text dataset script :) Resolved via #1913.