Refactor month box addition to grid pane.

Extracted repetitive code into the `addMonthBoxToGridPane` method. This improves the maintainability and readability of the `YearMonthViewSkin` class.

gemsfx/src/main/java/com/dlsc/gemsfx/skins/YearMonthViewSkin.java

@@ -64,18 +64,7 @@ public YearMonthViewSkin(YearMonthView control) {
 
         GridPane gridPane = new GridPane();
         gridPane.getStyleClass().add("grid-pane");
-        gridPane.add(new MonthBox(Month.JANUARY, control), 0, 0);
-        gridPane.add(new MonthBox(Month.FEBRUARY, control), 2, 0);
-        gridPane.add(new MonthBox(Month.MARCH, control), 0, 1);
-        gridPane.add(new MonthBox(Month.APRIL, control), 2, 1);
-        gridPane.add(new MonthBox(Month.MAY, control), 0, 2);
-        gridPane.add(new MonthBox(Month.JUNE, control), 2, 2);
-        gridPane.add(new MonthBox(Month.JULY, control), 0, 3);
-        gridPane.add(new MonthBox(Month.AUGUST, control), 2, 3);
-        gridPane.add(new MonthBox(Month.SEPTEMBER, control), 0, 4);
-        gridPane.add(new MonthBox(Month.OCTOBER, control), 2, 4);
-        gridPane.add(new MonthBox(Month.NOVEMBER, control), 0, 5);
-        gridPane.add(new MonthBox(Month.DECEMBER, control), 2, 5);
+        addMonthBoxToGridPane(gridPane, control);
 
         Region divider = new Region();
         divider.getStyleClass().add("divider");
@@ -131,6 +120,14 @@ public YearMonthViewSkin(YearMonthView control) {
         });
     }
 
+    private void addMonthBoxToGridPane(GridPane gridPane, YearMonthView control) {
+        for (Month month : Month.values()) {
+            int columnIndex = (month.getValue() % 2 == 0) ? 2 : 0;
+            int rowIndex = (month.getValue() - 1) / 2;
+            gridPane.add(new MonthBox(month, control), columnIndex, rowIndex);
+        }
+    }
+
     /**
      * Updates the pseudo-class state of the MonthBoxes.
      */