Correct Point file extensions in Codec javadocs (apache#13801)

lucene/core/src/java/org/apache/lucene/codecs/lucene912/package-info.java

@@ -306,7 +306,7 @@
  * </tr>
  * <tr>
  * <td>{@link org.apache.lucene.codecs.lucene90.Lucene90PointsFormat Point values}</td>
- * <td>.dii, .dim</td>
+ * <td>.kdd, .kdi, .kdm</td>
  * <td>Holds indexed points</td>
  * </tr>
  * <tr>
@@ -400,6 +400,8 @@
  *       performant encoding that is vectorized.
  *   <li>In version 8.6, index sort serialization is delegated to the sorts themselves, to allow
  *       user-defined sorts to be used
+ *   <li>In version 8.6, points fields split the index tree and leaf data into separate files, to
+ *       allow for different access patterns to the different data structures
  *   <li>In version 8.7, stored fields compression became adaptive to better handle documents with
  *       smaller stored fields.
  *   <li>In version 9.0, vector-valued fields were added.