Add a copy of the ASN.1 module to the appendix

I think this is the right syntax? Not that there's really much of an
ASN.1 module here at all. Closes #41

draft-beck-tls-trust-anchor-ids.md

@@ -594,6 +594,18 @@ The two mechanisms can be deployed together. An authenticating party can have me
 
 [[TODO: remove this or move to supporting documentation after more working group consensus]]
 
+# ASN.1 Module
+
+~~~
+TrustAnchorIdentifiers DEFINITIONS ::= BEGIN
+
+id-trustAnchorIdentifier OBJECT IDENTIFIER ::= { TBD }
+
+TrustAnchorIdentifier ::= RELATIVE-OID
+
+END
+~~~
+
 # Acknowledgements
 {:numbered="false"}