feat: backport mdx as known js source (#14560) (#14670)

Co-authored-by: Bjorn Lu <[email protected]>
Co-authored-by: Mark Dalgleish <[email protected]>

Author: 3 people

packages/vite/src/node/utils.ts

@@ -290,7 +290,8 @@ export const isDataUrl = (url: string): boolean => dataUrlRE.test(url)
 export const virtualModuleRE = /^virtual-module:.*/
 export const virtualModulePrefix = 'virtual-module:'
 
-const knownJsSrcRE = /\.(?:[jt]sx?|m[jt]s|vue|marko|svelte|astro|imba)(?:$|\?)/
+const knownJsSrcRE =
+  /\.(?:[jt]sx?|m[jt]s|vue|marko|svelte|astro|imba|mdx)(?:$|\?)/
 export const isJSRequest = (url: string): boolean => {
   url = cleanUrl(url)
   if (knownJsSrcRE.test(url)) {