ThirdParty: Add optional-lite polyfill

Thanks to all who have made contributions to
https://github.com/martinmoene/optional-lite

CMakeLists.txt

@@ -209,6 +209,10 @@ if(WIN32)
 	endif()
 endif(WIN32)
 
+# optional-lite
+add_subdirectory(third-party/optional-lite)
+target_link_libraries(icsneocpp PUBLIC optional-lite)
+
 if(${CMAKE_SYSTEM_NAME} STREQUAL "Darwin")
 	target_link_libraries(icsneocpp PUBLIC "-framework CoreFoundation" "-framework IOKit")
 endif()