add typed variant of MX example

diff --git a/examples/mx-typed.py b/examples/mx-typed.py
new file mode 100755 (executable)
index 0000000..41b7c98
--- /dev/null
+++ b/examples/mx-typed.py
@@ -0,0 +1,11 @@
+#!/usr/bin/env python3
+
+from typing import cast
+
+import dns.resolver
+from dns.rdtypes.ANY.MX import MX
+
+answers = dns.resolver.resolve("nominum.com", "MX")
+for rdata in answers:
+    mx_rdata = cast(MX, rdata)
+    print("Host", rdata.exchange, "has preference", rdata.preference)