termsupport: add support for tmux* $TERM values (#7622)

lib/termsupport.zsh

@@ -21,7 +21,7 @@ function title {
       print -Pn "\e]2;$2:q\a" # set window name
       print -Pn "\e]1;$1:q\a" # set tab name
       ;;
-    screen*)
+    screen*|tmux*)
       print -Pn "\ek$1:q\e\\" # set screen hardstatus
       ;;
     *)