/**
* DisplayChapter component displays a link or text for a chapter.
*
* By default will return a link with link text as eg: 'Chapter One' (ie:
* each word capitalised and numbers converted to words). Use
* props upper, lower, number as described to modify display
* of output.
* TODO: Check if chapter exists and display an error otherwise.
* TODO: Allow for chapters to exist in paths other than chapterDocPath
*
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