docs(nextjs): Add Next.js App Router pageload-SSR span linking limitation note

Author: RulaKhaled

docs/platforms/javascript/common/tracing/distributed-tracing/index.mdx

@@ -27,6 +27,16 @@ If you run any JavaScript applications in your distributed system, make sure tha
 
 </Alert>
 
+<PlatformSection supported={["javascript.nextjs"]}>
+
+<Alert>
+
+Pageload to SSR span linking is not supported on the App Router with Next.js versions up to and including 14.
+
+</Alert>
+
+</PlatformSection>
+
 ## How to Use Distributed Tracing?
 
 <PlatformContent includePath="distributed-tracing/how-to-use/" />