QtMqtt documentation cleanup

- Updated the overview documentation with details on how to link against
QtMqtt with CMake
- Added \qtcmakepackage command, to include CMake instructions in
class/namespace docs
- Removed the note about the module being part of Qt for Automation

Change-Id: Iac01f6e467915f6aedfc6324cf5faab104f768bf
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
Reviewed-by: Kai Koehne <kai.koehne@qt.io>
(cherry picked from commit ad8fe2f999)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/mqtt/doc/qtmqtt.qdocconf

@@ -39,7 +39,7 @@ excludedirs += ../qt4support
 
 Cpp.ignoretokens += Q_MQTT_EXPORT
 
-depends += qtcore qtdoc qtnetwork qmake qtwebsockets
+depends += qtcore qtdoc qtnetwork qmake qtwebsockets qtcmake
 
 #add generic thumbnail images for example documentation that does not have an image.
 manifestmeta.thumbnail.names  += "QtMqtt/WebSockets MQTT Subscription*"

src/mqtt/doc/src/index.qdoc

@@ -44,19 +44,16 @@
     and devices to publish telemetry data. The supported versions are MQTT 3.1,
     MQTT 3.1.1, and MQTT 5.0.
 
-    \note Qt MQTT is part of the Qt for Automation offering and not Qt. For further
-    details please see \l {Qt for Automation}.
-
-    \section1 Getting Started
-
-    To include the definitions of the module's classes, use the following
-    directive:
+    \include module-use.qdocinc using qt module
 
     \code
-    #include <QtMqtt/QtMqtt>
+    find_package(Qt6 REQUIRED COMPONENTS Mqtt)
+    target_link_libraries(mytarget PRIVATE Qt6::Mqtt)
     \endcode
 
-    To link against the module, add this line to your \l qmake \c .pro file:
+    See also the \l {Build with CMake} overview.
+
+    \include module-use.qdocinc building with qmake
 
     \code
     QT += mqtt

src/mqtt/doc/src/module.qdoc

@@ -30,19 +30,9 @@
     \module QtMqtt
     \title Qt MQTT C++ Classes
     \ingroup modules
+    \qtcmakepackage Mqtt
     \qtvariable mqtt
     \brief Provides classes that enable sending messages via the MQTT protocol.
 
-    To use these classes in your application, use the following include
-    statement:
-
-    \code
-    #include <QtMqtt/QtMqtt>
-    \endcode
-
-    To link against the module, add this line to your \l qmake \c .pro file:
-
-    \code
-    QT += mqtt
-    \endcode
+    The \l{Qt MQTT} page contains information about how to use the module.
 */