Expose libinput Button Scrolling Button Lock Enabled property

resources/default-config.kdl

@@ -53,6 +53,7 @@ input {
         // accel-profile "flat"
         // scroll-method "on-button-down"
         // scroll-button 273
+        // scroll-button-lock
         // middle-emulation
     }
 
@@ -219,13 +220,13 @@ layout {
         // radius. It has to assume that windows have square corners, leading to
         // shadow artifacts inside the CSD rounded corners. This setting fixes
         // those artifacts.
-        // 
+        //
         // However, instead you may want to set prefer-no-csd and/or
         // geometry-corner-radius. Then, niri will know the corner radius and
         // draw the shadow correctly, without having to draw it behind the
         // window. These will also remove client-side shadows if the window
         // draws any.
-        // 
+        //
         // draw-behind-window true
 
         // You can change how shadows look. The values below are in logical