Document display::gtk::zoom-to-fit.

info from: https://superuser.com/questions/1752209/qemu-zoom-to-fit-shortcut-or-cli-switch

Signed-off-by: Jan Kratochvil <jan@jankratochvil.net>

diff --git a/qemu-options.hx b/qemu-options.hx
index 88e93c6103..90acb31056 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2071,6 +2071,9 @@ SRST
         ``window-close=on|off`` : Allow to quit qemu with window close button
 
         ``show-menubar=on|off`` : Display the main window menubar, defaults to "on"
+
+        ``zoom-to-fit=on|off`` : Expand video output to the window size,
+                                 defaults to "off"
 
     ``curses[,charset=<encoding>]``
         Display video output via curses. For graphics device models

28.06.2023 13:23, Jan Kratochvil wrpte:
> Document display::gtk::zoom-to-fit.

Applied to my trivial-patches branch. Thank you!

/mjt