Add javadoc

Author: jordan-powers

server/src/main/java/org/elasticsearch/index/fielddata/MultiValuedSortedBinaryDocValues.java

@@ -15,6 +15,10 @@
 
 import java.io.IOException;
 
+/**
+ * Wrapper around {@link BinaryDocValues} to decode the typical multivalued encoding used by
+ * {@link org.elasticsearch.index.mapper.BinaryFieldMapper.CustomBinaryDocValuesField}.
+ */
 public class MultiValuedSortedBinaryDocValues extends SortedBinaryDocValues {
 
     BinaryDocValues values;