Import Sentry in middleware

packages/gitbook/src/middleware.ts

@@ -97,6 +97,9 @@ export type LookupResult = PublishedContentWithCache & {
  * The middleware also takes care of persisting the visitor authentication state.
  */
 export async function middleware(request: NextRequest) {
+    // Instrumentation is not loaded correctly...
+    await import('./sentry');
+
     const { url, mode } = getInputURL(request);
 
     setTag('url', url.toString());