Packaging Virtual keyboard via install script.

A request for packaging the virtual keyboard via the install script. Currently, when using qt_generate_deploy_qml_app_script to install, the installed program does not properly open the virtual keyboard.

To illustrate the current limitation,  build the attached project, and then install it using cpack and dpkg -i.

Specifying the plugin import path manually, as shown below, is necessary to have  virtual keyboard for the installed app.

set(VKB_OUTPUT_DIR "plugins")

get_target_property(Qt_virtualkeyboardplugin_location Qt6::QVirtualKeyboardPlugin LOCATION)
install(FILES ${Qt_virtualkeyboardplugin_location} DESTINATION ${VKB_OUTPUT_DIR}/platforminputcontexts)