Add a link to the reference implementation

Author: jedisct1

README.md

@@ -8,4 +8,5 @@ The Anonymized DNSCrypt extension prevents DNS servers from associating queries
 
 - [DNSCrypt v2](https://raw.githubusercontent.com/DNSCrypt/dnscrypt-protocol/master/DNSCRYPT-V2-PROTOCOL.txt)
 - [Anonymized DNSCrypt](https://raw.githubusercontent.com/DNSCrypt/dnscrypt-protocol/master/ANONYMIZED-DNSCRYPT.txt)
-- [DNSCrypt RFC](https://dnscrypt.github.io/dnscrypt-protocol/#go.draft-denis-dprive-dnscrypt.html) (WIP, editor's copy)
+- [DNSCrypt RFC](https://dnscrypt.github.io/dnscrypt-protocol/#go.draft-denis-dprive-dnscrypt.html) (WIP, editor's copy)
+- [Reference implementation](reference-implementation/) (Python)