Add a timeout: delay_exit_on_zero_displays

Outputs may disappear momentarily and come back later.
To prevent i3 from exit when no output is available momentarily, add a timeout delay_exit_on_zero_displays.

src/config_directives.c

@@ -329,6 +329,10 @@ CFGFUN(force_display_urgency_hint, const long duration_ms) {
     config.workspace_urgency_timer = duration_ms / 1000.0;
 }
 
+CFGFUN(delay_exit_on_zero_displays, const long duration_ms) {
+    config.zero_disp_exit_timer_ms = duration_ms;
+}
+
 CFGFUN(focus_on_window_activation, const char *mode) {
     if (strcmp(mode, "smart") == 0)
         config.focus_on_window_activation = FOWA_SMART;