docs: add DeepWiki badge to README (#684)

- Add DeepWiki badge for interactive documentation access
- Badge enables users to easily access AI-powered documentation assistant
- Positioned with other project badges for consistency

Author: imbajin

README.md

@@ -6,6 +6,7 @@
 [![Build Status](https://github.com/apache/hugegraph-toolchain/actions/workflows/hubble-ci.yml/badge.svg)](https://github.com/apache/hugegraph-toolchain/actions/workflows/hubble-ci.yml)
 [![Build Status](https://github.com/apache/hugegraph-toolchain/actions/workflows/tools-ci.yml/badge.svg)](https://github.com/apache/hugegraph-toolchain/actions/workflows/tools-ci.yml)
 [![Maven Central](https://maven-badges.herokuapp.com/maven-central/org.apache.hugegraph/hugegraph-client/badge.svg)](https://mvnrepository.com/artifact/org.apache.hugegraph/hugegraph-client)
+[![Ask DeepWiki](https://deepwiki.com/badge.svg)](https://deepwiki.com/apache/hugegraph-toolchain)
 
 `hugegraph-toolchain` is the integration project contains a series of utilities for [HugeGraph](https://github.com/apache/hugegraph), 
 it includes 5+ main modules.