Update README.md

Signed-off-by: hengm3467 <[email protected]>

README.md

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 This repository contains the latest RisingWave documentation. [The old repository](https://github.com/risingwavelabs/risingwave-docs-legacy) now hosts the archived documentation up to v2.0 of RisingWave.
 
+# Documentation structure
+
+Below are the main topic groups. Some groups are elevated to be tabs shown on the top of a documentation page.
+
+- get-started
+- demos
+- sql
+- ingestion
+- processing
+- delivery
+- deploy
+- operate
+- python-sdk
+- client-libraries
+- performance
+- troubleshoot
+- integrations
+- faq
+- reference
+- cloud
+- changelog
 
 
-# Mintlify Starter Kit
-
-Click on `Use this template` to copy the Mintlify starter kit. The starter kit contains examples including
-
-- Guide pages
-- Navigation
-- Customizations
-- API Reference pages
-- Use of popular components
-
 ### Development
 
 Install the [Mintlify CLI](https://www.npmjs.com/package/mintlify) to preview the documentation changes locally. To install, use the following command