dwindle: add swapsplit dispatcher (#4702)

This is distinct from `swapwindow` in that it allows swapping the entire
tree node with its neighbour.

Fixes: https://github.com/hyprwm/Hyprland/issues/4701

src/layout/DwindleLayout.hpp

@@ -83,6 +83,7 @@ class CHyprDwindleLayout : public IHyprLayout {
     SDwindleNodeData*       getMasterNodeOnWorkspace(const int&);
 
     void                    toggleSplit(CWindow*);
+    void                    swapSplit(CWindow*);
 
     eDirection              overrideDirection = DIRECTION_DEFAULT;