Comments about input queue being close to be supporting multi-thread. (#5772)

imgui.cpp

@@ -10483,6 +10483,8 @@ void ImGui::UpdateInputEvents(bool trickle_fast_inputs)
 #endif
 
     // Remaining events will be processed on the next frame
+    // FIXME-MULTITHREADING: io.AddKeyEvent() etc. calls are mostly thread-safe apart from the fact they push to this
+    // queue which may be resized here. Could potentially rework this to narrow down the section needing a mutex? (#5772)
     if (event_n == g.InputEventsQueue.Size)
         g.InputEventsQueue.resize(0);
     else