docs: Enabled mermaid chart support for docs (#4433)

# What does this PR do?
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relevant issues if applicable. -->
- Before the fix

<img width="1253" height="926" alt="Screenshot 2025-12-29 at 1 02 36 PM"
src="https://github.com/user-attachments/assets/5321c265-9aef-4f6e-98f1-ebc7530e9934"
/>

- After fix

<img width="1315" height="927" alt="Screenshot 2025-12-29 at 1 03 03 PM"
src="https://github.com/user-attachments/assets/66382c7f-038d-4951-83b9-314e014390b2"
/>


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<!-- Closes #[issue-number] -->

## Test Plan
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summaries. *Provide clear instructions so the plan can be easily
re-executed.* -->

docs/package.json

@@ -21,6 +21,7 @@
   "dependencies": {
     "@docusaurus/core": "3.8.1",
     "@docusaurus/preset-classic": "3.8.1",
+    "@docusaurus/theme-mermaid": "3.8.1",
     "@easyops-cn/docusaurus-search-local": "^0.52.1",
     "@mdx-js/react": "^3.0.0",
     "clsx": "^2.0.0",