feat: add MDX file support (#12261)

Feat: add MDX file support  #12057 
### What problem does this PR solve?

<img width="1055" height="270" alt="image"
src="https://github.com/user-attachments/assets/a0ab49f9-7806-41cd-8a96-f593591ab36b"
/>

The page states that MDX files are supported, but uploading fails with
the error: "x.mdx: This type of file has not been supported yet!"
<img width="381" height="110" alt="image"
src="https://github.com/user-attachments/assets/4bbb7d08-cb47-416a-95fc-bc90b90fcc39"
/>


### Type of change

- [x] New Feature (non-breaking change which adds functionality)

web/src/pages/chunk/parsed-result/add-knowledge/components/knowledge-chunk/index.tsx

@@ -172,6 +172,7 @@ const Chunk = () => {
       case 'docx':
       case 'txt':
       case 'md':
+      case 'mdx':
       case 'pdf':
         return documentInfo?.type;
     }

web/src/pages/dataflow-result/index.tsx

@@ -87,6 +87,7 @@ const Chunk = () => {
       case 'docx':
       case 'txt':
       case 'md':
+      case 'mdx':
       case 'pdf':
         return documentInfo?.type;
     }

web/src/pages/document-viewer/index.tsx

@@ -40,7 +40,9 @@ const DocumentViewer = () => {
           <ImagePreviewer className="w-full !h-dvh p-5" url={api} />
         </div>
       )}
-      {ext === 'md' && <Md url={api} className="!h-dvh p-5"></Md>}
+      {(ext === 'md' || ext === 'mdx') && (
+        <Md url={api} className="!h-dvh p-5"></Md>
+      )}
       {ext === 'txt' && <TxtPreviewer url={api}></TxtPreviewer>}
 
       {ext === 'pdf' && (