typed STD_PROPERTIES to Collection and used List.of !6

simpleexample2/core/src/main/java/simpleex/core/MetaData.java

@@ -21,7 +21,7 @@ public class MetaData {
   /**
    * the list containing standard properties associated to location metadata
    */
-  public final static List<String> STD_PROPERTIES = Collections.unmodifiableList(Arrays.asList(NAME_PROPERTY, DESCRIPTION_PROPERTY));
+  public final static Collection<String> STD_PROPERTIES = List.of(NAME_PROPERTY, DESCRIPTION_PROPERTY);
  
   
   private Collection<String> tags;