Updated CPython example to use port 5000 by default and added explanation for that

Author: michalpokusa

examples/httpserver_cpython.py

@@ -19,4 +19,6 @@ def base(request: Request):
     return Response(request, "Hello from the CircuitPython HTTP Server!")
 
 
-server.serve_forever("0.0.0.0")
+# Ports below 1024 are reserved for root user only.
+# If you want to run this example on a port below 1024, you need to run it as root (or with `sudo`).
+server.serve_forever("0.0.0.0", 5000)