updated style

src/main/java/ch/zhaw/gartenverwaltung/PlantsController.java

@@ -25,6 +25,7 @@ import javafx.scene.layout.VBox;
 import java.io.IOException;
 import java.time.LocalDate;
 import java.util.List;
+import java.util.Objects;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -82,6 +83,10 @@ public class PlantsController {
 
         DialogPane dialogPane = dateSelection.getDialogPane();
 
+        dialogPane.getStylesheets().add(
+                Objects.requireNonNull(getClass().getResource("bootstrap/dialogStyle.css")).toExternalForm());
+        dialogPane.getStyleClass().add("myDialog");
+
         ButtonType sowButton = new ButtonType("Save", ButtonBar.ButtonData.OK_DONE);
         dialogPane.getButtonTypes().addAll(sowButton, ButtonType.CANCEL);