Update: add initial handling of zero-width space in FSS projects

Update: add initial handling of zero-width space in FSS projects

UTF-8 zero-width characters have the potential for being combining characters.
In such cases, the combiner/joiner should be considered part of what is being combined.
That is a combiner/joiner before a graph should be treated as a graph.
A combiner/joiner before a whitespace should be treated as a whitespace.

Disclaimer: I suspect that this will eventually need to be broken down to handle each specific case.
A combiner/joiner on whitespace that results in rendering a printable/visible character would be a violation of the whitespace design principles of FSS.
Further investigation is needed and will likely require changes.

Add appropriate @todo for further development of this functionality.

Rename max_width to width_max to follow newer practices.