The bold+italic combination indicated by ***triple stars*** requires
this; but it enables combinations of italics, bold, strikeout, anchor
text (and associated link formatting), image alternate text, and inline
code formatting (monospace). A code span overrides the formatting from
surrounding spans (which might be a bug to fix in another patch, if we
compare to how md2html formats code nested in bold-italics for example),
but the format stack restores state when any char format span ends.
Task-number: QTBUG-81306
Pick-to: 5.15
Change-Id: I289556fa53de400eb50a4d159b9b344eafc517da
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
3373aa8b35