fix syntax highlight in modernjs.mdx (#3425)

Author: NookieGrey

apps/website-new/docs/en/guide/framework/modernjs.mdx

@@ -182,7 +182,7 @@ Note: This component only renders this fault-tolerant component on the client si
 
 If the current project only needs to load MF in the CSR, you can set `ssr: false` to help progressive migration.
 
-```title='modern.config.ts'
+```ts title='modern.config.ts'
 import { appTools, defineConfig } from '@modern-js/app-tools';
 import { moduleFederationPlugin } from '@module-federation/modern-js';