Don't erase urgency hint instantly

Make it easier to realize which window raised it.

dotfiles/i3/config

@@ -66,6 +66,7 @@ hide_edge_borders vertical
 font pango:Inconsolata 12
 workspace_layout stacked
 workspace_auto_back_and_forth yes
+force_display_urgency_hint 500 ms
 
 # change focus
 bindsym $mod+h              focus left