docs: add architecture (#237)

Author: sykp241095

frontend/app/src/pages/docs/faq.mdx

@@ -18,6 +18,13 @@ export function FAQBox({ title, children }) {
   )
 }
 
+
+<FAQBox title="What's the artechitecture or workflow of this Graph RAG app?">
+
+![Graph RAG app architecture](https://github.com/user-attachments/assets/a21e1bb7-3a9f-49ed-aa6a-de8be0ada17f)
+
+</FAQBox>
+
 <FAQBox title="Is this RAG app free?">
 - The code of this RAG app is open source, it's free to use;
 - The database of this RAG app is free for **25GiB storage** as we use [TiDB Serverless](https://tidb.cloud);
@@ -41,4 +48,4 @@ export function FAQBox({ title, children }) {
 - [Change Default Reranker](/docs/reranker)
 - [Change Default Embedding API](/docs/embedding)
 
-</FAQBox>
+</FAQBox>