Add a function that minimizes the Android app (#692)

Add a function that minimizes the Android app

client/ui/controllers/pageController.cpp

@@ -7,6 +7,7 @@
 #endif
 
 #ifdef Q_OS_ANDROID
+    #include "platforms/android/android_controller.h"
     #include "platforms/android/android_utils.h"
     #include <QJniObject>
 #endif
@@ -74,6 +75,13 @@ void PageController::closeWindow()
 #endif
 }
 
+void PageController::hideWindow()
+{
+#ifdef Q_OS_ANDROID
+    AndroidController::instance()->minimizeApp();
+#endif
+}
+
 void PageController::keyPressEvent(Qt::Key key)
 {
     switch (key) {