doc: add v16 changelog link to iojs changelog

PR-URL: #41808
Reviewed-By: Richard Lau <[email protected]>
Reviewed-By: Antoine du Hamel <[email protected]>
Reviewed-By: Mestery <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Beth Griggs <[email protected]>

Author: danielleadams

doc/changelogs/CHANGELOG_IOJS.md

@@ -63,6 +63,7 @@
 
 * Other Versions
   * [17.x](CHANGELOG_V17.md)
+  * [16.x](CHANGELOG_V16.md)
   * [15.x](CHANGELOG_V15.md)
   * [14.x](CHANGELOG_V14.md)
   * [13.x](CHANGELOG_V13.md)