Resurrect "focus child" under Shift+A (comp. A for "focus parent")

dotfiles/i3/config

 
 # focus the parent container
 bindsym $mod+a focus parent
-
-# focus the child container
-#bindsym $mod+d focus child
+bindsym $mod+Shift+a focus child
 
 # assign workspace names
 set $w1 1