Add server sent events design TODO

design.md

@@ -105,6 +105,7 @@ See `config.md` for complete configuration documentation.
 - **Safe shutdown mechanism** with async-signal-safe shutdown() method
 - **Connection ownership management** with automatic cleanup on server destruction
 - **Pluggable protocol handlers** via ConnectionHandler interface
+- TODO design a way to stream server sent events
 
 Key features:
 - Multi-threaded architecture: separate accept and network thread pools