Mention seventh anchor line 'baseline' in the documentation

Change-Id: I5b3487d0f56980d057c34438a877a6626fe535a3
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

doc/src/qmlapp/usecases/layouts.qdoc

@@ -50,9 +50,11 @@ accomplished by setting the x and y coordinates to the appropriate bindings.
 
 \section1 Anchors
 
-The \c Item type provides the abilitiy to anchor to other \l Item types. There are six anchor lines for each item: \e left,
-\e right, \e{vertical center}, \e top, \e bottom and \e{horizontal center}. The three vertical anchor lines can be anchored to any of
-the three vertical anchor lines of another item, and the three horizontal anchor lines can be anchored to the
+The \c Item type provides the abilitiy to anchor to other \l Item types. There
+are seven anchor lines for each item: \e left, \e right, \e{vertical center},
+\e top, \e bottom, \e baseline and \e{horizontal center}. The three vertical
+anchor lines can be anchored to any of the three vertical anchor lines of
+another item, and the four horizontal anchor lines can be anchored to the
 horizontal anchor lines of another item.
 
 For full details, see \l {Positioning with Anchors} and the documentation of the \l{Item::anchors.top}{anchors property}.