Document QJniObject::construct

Added for 6.4. Not extremely useful as long as the macros that allow
the declaration of new class and type strings also being documented.

Change-Id: I9ee466fdd0aaccec1e627ceb313b5a5c17e3f3fa
Reviewed-by: BogDan Vatra <bogdan@kdab.com>
(cherry picked from commit 145bfe6054f8f7fcc32d0442e8845aa59af2fc1a)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/kernel/qjniobject.cpp

@@ -761,6 +761,21 @@ QJniObject::QJniObject(jobject object)
     env->DeleteLocalRef(cls);
 }
 
+/*!
+    \fn template<typename Class, typename ...Args> static inline QJniObject construct(Args &&...args)
+    \since 6.4
+
+    Constructs an instance of the Java class that is the equivalent of \c Class and
+    returns a QJniObject containing the JNI object. The arguments in \a args are
+    passed to the Java constructor.
+
+    \code
+    QJniObject javaString = QJniObject::construct<jstring>();
+    \endcode
+
+    This function is only available if all \a args are known \l {JNI Types}.
+*/
+
 /*!
     \brief Get a JNI object from a jobject variant and do the necessary
     exception clearing and delete the local reference before returning.