Add stretching of modules and modules-center toggling

This Patch allows the stretching of modules-{left,center,right} as well
add a "expand" flag to AModule. This allows one module to consume the
leftover space.
To allow the left or right modules to fully consume the center, the
changes also include a way to remove the center box (center_)
altogether.

man/waybar-hyprland-submap.5.scd

@@ -93,6 +93,11 @@ Addressed by *hyprland/submap*
 	typeof: array ++
 	The actions corresponding to the buttons of the menu.
 
+*expand*: ++
+	typeof: bool ++
+	default: false ++
+	Enables this module to consume all left over space dynamically.
+
 
 # EXAMPLES