Add Newline Character Handling to nk_text/nk_label

[zgcrowno]

This is a newline handling implementation originally written by @AntiBlueQuirk, but which was never merged into the old Vurtun library for some reason. I've been very pleased with the results so far, but would obviously love feedback on potential issues I may have overlooked when bringing over this implementation.

[Hejsil]

I haven't tested the code, but I've read through it. The code looks good to me though :+1:

[zgcrowno]

Thanks for taking the time to look this over, @Hejsil!

[zgcrowno]

@dumblob, is this functionality something you're still interested in?

[krupitskas]

Ehm, it's pretty important feature and this is march 2021, feels like this repo died

[dumblob]

I'll chime in quickly just to say I'm sorry for not devoting any time lately to Nuklear (I'm too busy with family life).

I'd like to say though, that I don't think this repo is dead. It's just slow. Any new reviewers are welcome (after a good review or two they'll get full access to this repository and are encouraged to recruit other new reviewers).

[dumblob]

Seeing this at this time I'm playing with the idea to declare the current behavior of nk_text_wrap and nk_widget_text_wrap as faulty and just change their behavior to not only wrap on newlines but also on word boundaries. Instead of providing yet another API (multiline functions) which'll presumably subsume probably all existing use cases of the wrap functions.

Thoughts?