Add documentation for the QTextBlockFormat::marker property

Amends 65314b6ce8.

Change-Id: I8f69030accb948055b0081f8a4f1daafbac824ce
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

src/gui/text/qtextformat.cpp

@@ -2337,6 +2337,50 @@ QList<QTextOption::Tab> QTextBlockFormat::tabPositions() const
 */
 
 
+/*!
+    \fn void QTextBlockFormat::setMarker(MarkerType marker)
+    \since 5.14
+
+    Sets the type of adornment that should be rendered alongside the paragraph to \a marker.
+    For example, a list item can be adorned with a checkbox, either checked
+    or unchecked, as a replacement for its bullet. The default is \c NoMarker.
+
+    \sa marker()
+*/
+
+
+/*!
+    \fn MarkerType QTextBlockFormat::marker() const
+    \since 5.14
+
+    Returns the paragraph's marker if one has been set, or \c NoMarker if not.
+
+    \sa setMarker()
+*/
+
+
+/*!
+    \since 5.14
+    \enum QTextBlockFormat::MarkerType
+
+    This enum describes the types of markers a list item can have.
+    If a list item (a paragraph for which \l QTextBlock::textList() returns the list)
+    has a marker, it is rendered instead of the normal bullet.
+    In this way, checkable list items can be mixed with plain list items in the
+    same list, overriding the type of bullet specified by the
+    \l QTextListFormat::style() for the entire list.
+
+    \value NoMarker This is the default: the list item's bullet will be shown.
+    \value Unchecked Instead of the list item's bullet, an unchecked checkbox will be shown.
+    \value Checked Instead of the list item's bullet, a checked checkbox will be shown.
+
+    In the future, this may be extended to specify other types of paragraph
+    decorations.
+
+    \sa QTextListFormat::style()
+*/
+
+
 /*!
     \fn void QTextBlockFormat::setLineHeight(qreal height, int heightType)
     \since 4.8