Add a --border flag to enable mouse binds to trigger on border click

include/data.h

@@ -255,6 +255,10 @@ struct Binding {
         B_UPON_KEYRELEASE_IGNORE_MODS = 2,
     } release;
 
+    /** If this is true for a mouse binding, the binding should be executed
+     * when the button is pressed over the window border. */
+    bool border;
+
     /** If this is true for a mouse binding, the binding should be executed
      * when the button is pressed over any part of the window, not just the
      * title bar (default). */