Upgrade README

Signed-off-by: Thibault Meyer <meyer.thibault@gmail.com>

README.md

@@ -149,6 +149,8 @@ choose the one that seems best suited to you (crontab, gnome start at launch, et
 
 * [LINUX] Only Gnome is natively supported, to use this application with another Desktop
   Environment, you have to use `exec_apply_wallpaper` option in the configuration file
+* [MAC] Sometime, "Dock" refuse to refresh wallpaper when you are using an application 
+  in fullscreen when bingwallpaper try to update wallpaper
 * [WINDOWS] Parameter `--nowindow` (or `-w`) not working if you use Terminal as default
   console. Terminal don't honor Windows API and don't allow application to detach from
   terminal. As workaround, you could create a shortcut and configure it to enable the