Beginner-level documentation

[sjakobi]

This request on r/haskellquestions indicates that bytestring should be more accessible for Haskell beginners.

To improve the situation, I suggest we add:

• Doctest-style (>>>) examples on most functions.

  • To avoid excessive visual noise, the examples should be in collapsible ==== __Examples__ sections

• A (brief) tutorial, ideally as a tutorial module.