add reference to unicode emoji modifiers list

Author: vsch

flexmark-ext-emoji/src/main/javadoc/overview.md

@@ -1,13 +1,16 @@
 flexmark-java extension for emoji shortcuts
 
-emoji shortcut conversion: 
+emoji shortcut conversion:
 
-* [Emoji Cheat Sheet] shortcuts 
+* [Emoji Cheat Sheet] shortcuts
 * [GitHub Emoji API] shortcuts
-* any of the above shortcuts to [Unicode Emoji List, v11.0] Unicode Characters.
+* any of the above shortcuts to [Unicode Emoji List, v15.0] or [Unicode Emoji Modifiers List, v15.0] Unicode Characters.
 
 [`emoji-cheat-sheet.com/public/graphics/emojis/`]: https://github.com/WebpageFX/emoji-cheat-sheet.com/tree/master/public/graphics/emojis
 [GitHub Emoji API]: https://api.github.com/emojis
-[Unicode Emoji List, v11.0]: https://unicode.org/emoji/charts/emoji-list.html
+[Unicode Emoji List, v15.0]: https://unicode.org/emoji/charts/emoji-list.html
+<!-- @IGNORE PREVIOUS: link -->
+[Unicode Emoji Modifiers List, v15.0]: https://unicode.org/emoji/charts/full-emoji-modifiers.html
+<!-- @IGNORE PREVIOUS: link -->
 [Emoji Cheat Sheet]: https://github.com/WebpageFX/emoji-cheat-sheet.com