feat: diagrams can be rendered using Mermaid in a code block (#458)

### What this PR does?
添加对 Mermaid Diagrams 的支持

```release-note
None
```

docusaurus.config.js

@@ -15,6 +15,10 @@ const config = {
   },
   organizationName: "halo-dev", // Usually your GitHub org/user name.
   projectName: "halo", // Usually your repo name.
+  markdown: {
+    mermaid: true,
+  },
+  themes: ['@docusaurus/theme-mermaid'],
 
   presets: [
     [