add: configuration options and keybinds for the dual-scroller layout

config.conf

@@ -57,6 +57,7 @@ scroller_prefer_center=0
 edge_scroller_pointer_focus=1
 scroller_default_proportion_single=1.0
 scroller_proportion_preset=0.5,0.8,1.0
+dual_scroller_default_split_ratio=0.3
 
 # Master-Stack Layout Setting
 new_is_master=1
@@ -237,6 +238,10 @@ bind=CTRL+ALT,Down,resizewin,+0,+50
 bind=CTRL+ALT,Left,resizewin,-50,+0
 bind=CTRL+ALT,Right,resizewin,+50,+0
 
+# dual-scroller split adjustment (increase/decrease top row height)
+# bind=SUPER+SHIFT,Equal,adjust_dual_scroller_split,0.05
+# bind=SUPER+SHIFT,Minus,adjust_dual_scroller_split,-0.05
+
 # Mouse Button Bindings
 # NONE mode key only work in ov mode
 mousebind=SUPER,btn_left,moveresize,curmove