Fix: Alignment for background opacity percentage label

Author: KSSJW

HMCL/src/main/java/org/jackhuang/hmcl/ui/main/PersonalizationPage.java

@@ -1007,6 +1007,7 @@ protected Node createRightNode() {
 
                 Label textOpacity = new Label();
                 FXUtils.setLimitWidth(textOpacity, 50);
+                textOpacity.setAlignment(Pos.CENTER);
 
                 StringBinding valueBinding = Bindings.createStringBinding(() -> ((int) slider.getValue()) + "%", slider.valueProperty());
                 textOpacity.textProperty().bind(valueBinding);