docs: add warning message

Signed-off-by: Wing-Kam Wong <wingkwong.code@gmail.com>

packages/noco-docs-prev/content/en/index.md

@@ -1,11 +1,16 @@
 ---
-title: 'NocoDB Documentation'
-description: 'NocoDB Documentation'
+title: 'NocoDB Documentation (Previous Versions)'
+description: 'NocoDB Documentation (Previous Versions)'
 position: 0
 category: 'Welcome'
 menuTitle: 'Introduction'
 ---
 
+<alert type="warning">
+If you are using NocoDB with version 0.90 onwards, please check out the latest documentation <a href="#" target="_blank">here</a> instead. <br/> The previous version is no longer maintained and will be completely deprecated on 30 Jun 2022. <br/> See <a href="https://github.com/nocodb/nocodb/issues/1564" target="_blank">v0.90 Important Announcement</a> for more.
+</alert>
+
+
 ## Welcome!
 
 NocoDB is an open source Airtable alternative.