[fix] correct link to a live demo in README.md

AlexKlimenkov · AlexKlimenkov · commit ced368dd41bd · 2019-06-27T18:56:16.000+03:00
diff --git a/README.md b/README.md
@@ -47,7 +47,7 @@ gantt.parse({
 });
 ~~~
 
-==> [Check the live demo](http://snippet.dhtmlx.com/488b9857e)
+==> [Check the live demo](https://snippet.dhtmlx.com/a69d7378a)
 
 ### Complete guides
 
