Add a heading for the info on installing Qt in Getting Started

Change-Id: I7227674a7677a12b04f72e6989909cc5220968e7
Reviewed-by: Venugopal Shivashankar <Venugopal.Shivashankar@qt.io>

doc/src/getting-started/gettingstarted.qdoc

@@ -30,6 +30,8 @@
     \title Getting Started with Qt
     \brief A quick guide for developers
 
+    \section1 Install Qt
+
     You can install the Qt Framework and tools by using an online or offline
     installer or by building the source packages yourself. In the
     \e{online installer}, you can select the Qt versions, tools, and Add-On