fix import for central openminds class

Author: olinux

generator/templates/OpenMINDS.java.j2

@@ -8,6 +8,7 @@ import org.openmetadatainitiative.openminds.utils.LocalId;
 
 import java.io.File;
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.stream.Stream;