Doc: Describe adding the import path

Also add the import path to the example main.cpp file.

Task-number: QDS-805
Change-Id: I990e5dc364d610a4cef5697b3355147f9e5fcde1
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

doc/examples/progressbar/main.cpp

@@ -9,6 +9,7 @@ int main(int argc, char *argv[])
     QGuiApplication app(argc, argv);
 
     QQuickView view;
+    view.engine->addImportPath("qrc:/qml/imports");
     view.setSource(QUrl("qrc:/qml/ProgressBar.ui.qml"));
     if (!view.errors().isEmpty())
         return -1;

doc/src/qtquick/qtquick-from-qmlproject-to-pro.qdoc

@@ -99,8 +99,9 @@
             \quotefromfile progressbar/main.cpp
             \skipto QQuickView view;
             \printuntil view.show()
-            Where \c {qml\main.qml} is the path to and the name of the main QML
-            file in the Qt Quick UI project.
+            Where \c {qrc:/qml/imports} is the import path and
+            \c {qrc:qml/ProgressBar.ui.qml} is the path to and the
+            name of the main QML file in the Qt Quick UI project.
         \li Select \uicontrol Build > \uicontrol Run to build and run your
             project.
     \endlist