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/constants/common.ts

@@ -18,6 +18,8 @@ export const fileIconMap = {
   jpg: 'jpg.svg',
   js: 'js.svg',
   json: 'json.svg',
+  md: 'md.svg',
+  mdx: 'mdx.svg',
   mkv: 'mkv.svg',
   mp3: 'mp3.svg',
   mp4: 'mp4.svg',
@@ -142,6 +144,8 @@ export enum FileMimeType {
   Xlsx = 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
   Mp4 = 'video/mp4',
   Json = 'application/json',
+  Md = 'text/markdown',
+  Mdx = 'text/markdown',
 }
 
 export const Domain = 'demo.ragflow.io';
@@ -161,7 +165,15 @@ export const Images = [
 ];
 
 // Without FileViewer
-export const ExceptiveType = ['xlsx', 'xls', 'pdf', 'docx', 'md', ...Images];
+export const ExceptiveType = [
+  'xlsx',
+  'xls',
+  'pdf',
+  'docx',
+  'md',
+  'mdx',
+  ...Images,
+];
 
 export const SupportedPreviewDocumentTypes = [...ExceptiveType];
 //#endregion

web/src/constants/file.ts

@@ -12,6 +12,7 @@ export const FileIconMap = {
   txt: 'text',
   csv: 'pdf',
   md: 'md',
+  mdx: 'md',
   mp4: 'mp4',
   avi: 'avi',
   mkv: 'mkv',