Make default formatter compatible with screenreader

Problem/Motivation

Initially the screenreader formatter was separate from the default formatter. I think I figured out a way to make the default formatter compatible with screenreaders, in which case I can and should remove the separate screenreader formatter.

This will remove the crossword_screenreader formatter along with any related templates, libraries, theme suggestions, and tests. This will end up increasing the power of the module while making it easier to maintain and use.