fix(demo): add blur mode to number field

Close #11

src/test/java/com/flowingcode/vaadin/addons/whatsappbutton/WhatsappButtonDemo.java

@@ -104,6 +104,7 @@ private IntegerField createIntegerField(String placeholder) {
     IntegerField integerField = new IntegerField();
     integerField.setPlaceholder(placeholder);
     integerField.setClearButtonVisible(true);
+    integerField.setValueChangeMode(ValueChangeMode.ON_BLUR);
     return integerField;
   }