feat: export BlitzServerMiddleware from blitz-next (#4296)

* feat: export `BlitzServerMiddleware` from blitz-next

* Create sixty-pants-hunt.md

---------

Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

Author: siddhsuresh

.changeset/sixty-pants-hunt.md

@@ -0,0 +1,6 @@
+---
+"@blitzjs/next": patch
+"blitz": patch
+---
+
+feat: export `BlitzServerMiddleware` from blitz-next with stronger types

packages/blitz-next/src/index-server.ts

@@ -22,6 +22,7 @@ import {
   RouteUrlObject,
   startWatcher,
   stopWatcher,
+  RequestMiddleware,
 } from "blitz"
 import {
   getInfiniteQueryKey,
@@ -347,3 +348,15 @@ declare module "blitz" {
     prefetchInfiniteQuery: PrefetchQueryFn
   }
 }
+
+export const BlitzServerMiddleware = <
+  TMiddleware extends RequestMiddleware<NextApiRequest, BlitzNextApiResponse> = RequestMiddleware<
+    NextApiRequest,
+    BlitzNextApiResponse
+  >,
+>(
+  middleware: TMiddleware,
+): BlitzServerPlugin<{}> => ({
+  requestMiddlewares: [middleware],
+  exports: () => ({}),
+})