add parser config for empty_workspaces config variable

parser-specs/config.spec

@@ -40,6 +40,7 @@ state INITIAL:
   'assign'                                 -> ASSIGN
   'no_focus'                               -> NO_FOCUS
   'focus_follows_mouse'                    -> FOCUS_FOLLOWS_MOUSE
+  'empty_workspaces'                       -> EMPTY_WORKSPACES
   'mouse_warping'                          -> MOUSE_WARPING
   'focus_wrapping'                         -> FOCUS_WRAPPING
   'force_focus_wrapping'                   -> FORCE_FOCUS_WRAPPING
@@ -269,6 +270,11 @@ state FOCUS_FOLLOWS_MOUSE:
   value = word
       -> call cfg_focus_follows_mouse($value)
 
+# empty_workspaces bool
+state EMPTY_WORKSPACES:
+  value = word
+      -> call cfg_empty_workspaces($value)
+
 # mouse_warping warping_t
 state MOUSE_WARPING:
   value = 'none', 'output'