[add] a note for suite 5 docs

Author: mafanya23

docs/index.md

@@ -102,3 +102,9 @@ All DHTMLX widgets are created with accessible design in mind. DHTMLX sticks to
 ## Release History
 
 The list of all DHTMLX Suite versions including maintenance, minor, and major releases is available in the ["What's new"](/whatsnew/) section of the documentation. If you are using an older version of DHTMLX Suite than the current one, the [migration guide](/migration/) will instruct you on the changes in the code.
+
+## Documentation for DHTMLX Suite 5 version 
+
+:::info
+If you are using an outdated version of DHTMLX Suite 5 and require the documentation for it, please [contact us](https://dhtmlx.com/docs/contact.shtml), and we will send it to you.
+:::