add namespace for cmake export

CMakeLists.txt

@@ -172,5 +172,5 @@ install(FILES
         ${CMAKE_BINARY_DIR}/${CMAKE_PROJECT_NAME}Config.cmake
         DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${CMAKE_PROJECT_NAME})
 
-install(EXPORT ${CMAKE_PROJECT_NAME}Targets
+install(EXPORT ${CMAKE_PROJECT_NAME}Targets NAMESPACE tinyxml2::
         DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${CMAKE_PROJECT_NAME})