updated code to follow brief's format better and tested save and open functionality

src/main/java/cvbuilder/controller/CsvExportSettings.java

@@ -5,7 +5,7 @@ import java.util.Map;
 
 public class CsvExportSettings {
     private static CsvExportSettings instance;
-    private Map<String, Boolean> includeMap = new HashMap<>();
+    private final Map<String, Boolean> includeMap = new HashMap<>();
 
     private CsvExportSettings() {
         // Initialize default values for all fields to be included