Expose NVQ from its graph feature (#693)

Signed-off-by: Akash Shankaran <akash.shankaran1@gmail.com>

Author: akash-shankaran

jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/NVQ.java

@@ -88,6 +88,10 @@ public State(QuantizedVector vector) {
         }
     }
 
+    public NVQuantization getNVQuantization() {
+        return nvq;
+    }
+
     public ScoreFunction.ExactScoreFunction rerankerFor(VectorFloat<?> queryVector,
                                                         VectorSimilarityFunction vsf,
                                                         FeatureSource source) {