update RFC section in readme

README.md

@@ -123,6 +123,7 @@ Zones will be automatically resigned on any record updates via dynamic DNS.
 - [RFC 4035](https://tools.ietf.org/html/rfc4035): Protocol Modifications for DNSSEC
 - [RFC 4509](https://tools.ietf.org/html/rfc4509): SHA-256 in DNSSEC Delegation Signer
 - [RFC 5702](https://tools.ietf.org/html/rfc5702): SHA-2 Algorithms with RSA in DNSKEY and RRSIG for DNSSEC
+- [RFC 6844](https://tools.ietf.org/html/rfc6844): DNS Certification Authority Authorization (CAA) Resource Record
 - [RFC 6698](https://tools.ietf.org/html/rfc6698): The DNS-Based Authentication of Named Entities (DANE) Transport Layer Security (TLS) Protocol: TLSA
 - [RFC 6840](https://tools.ietf.org/html/rfc6840): Clarifications and Implementation Notes for DNSSEC
 - [RFC 6844](https://tools.ietf.org/html/rfc6844): DNS Certification Authority Authorization Resource Record