Doc: Add information about building the module with CMake

Task-number: QTBUG-81560
Change-Id: I9d75606634da4c604f34913908f97a91797d1813
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
Reviewed-by: Leander Beernaert <leander.beernaert@qt.io>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

src/pdf/doc/qtpdf.qdocconf

@@ -39,7 +39,8 @@ depends += qtcore \
            qtdoc \
            qmake \
            qtdesigner \
-           qtquick
+           qtquick \
+           qtcmake
 
 headerdirs  += ../api \
                ../quick

src/pdf/doc/snippets/qtpdf-build.cmake

+find_package(Qt5 COMPONENTS Pdf REQUIRED)
+target_link_libraries(mytarget Qt5::Pdf)

src/pdf/doc/src/qtpdf-index.qdoc

@@ -39,7 +39,12 @@
     \l QPdfPageNavigation class handles the navigation through a
     PDF document.
 
-    \section1 Getting Started
+    \include module-use.qdocinc using qt module
+    \quotefile qtpdf-build.cmake
+
+    See also the \l{Build with CMake} overview.
+
+    \section2 Building with qmake
 
     To include the definitions of the module's classes, use the
     following directive: