Edit TODO using wlist with select.select()

Under heavy charge the script might be weak with seocket.read() &
socket.send() using together rlist in select.select().
See https://pymotw.com/3/select/index.html

chat/TODO.md

@@ -11,4 +11,5 @@
 - [ ] client freeze when sending empty string or spaces
 - [ ] clean the prompt and std.out a bit messy since broadcasting
 - [ ] move closing connection at the script's end
+- [ ] using wlist with select.select for hardening the script
 - [ ] …