docs: add afgo extension mention to readme (#312)

Signed-off-by: Troy Ronda <troy.ronda@securekey.com>

Signed-off-by: Troy Ronda <troy.ronda@securekey.com>

Author: troyronda

README.md

@@ -3,6 +3,10 @@
 Hyperledger Aries Framework Go enables trusted communication and data exchange based on interoperable distributed ledger technologies (DLTs) and peer-to-peer (P2P) interactions.
 We provide a flexible toolkit to enable the usage of decentralized identifiers (DIDs), DID-to-DID communications, verifiable credential exchange, transaction authorizations, and data communication protocols. From these building blocks, implementors can build agents, mediators and other DIDComm features in a manner that is agnostic to a particular DID network or governance framework.
 
+## Aries Framework Go Extensions
+
+This repository contains extension modules for [Hyperledger Aries Framework Go](https://github.com/hyperledger/aries-framework-go).
+
 ## Contributing
 Found a bug? Ready to submit a PR? Want to submit a proposal for your grand
 idea? Follow our [guidelines](CONTRIBUTING.md) for more information