chore: add link to ADR 008 in godoc

modules/core/exported/packet.go

@@ -20,9 +20,11 @@ type Acknowledgement interface {
 	Acknowledgement() []byte
 }
 
-// CallbackPacketData defines the interface used by ADR 8 implementations
+// CallbackPacketData defines the interface used by ADR 008 implementations
 // to obtain callback addresses associated with a specific packet data type.
 // This is an optional interface which indicates support for ADR 8 implementations.
+// See https://github.com/cosmos/ibc-go/tree/main/docs/architecture/adr-008-app-caller-cbs
+// for more information.
 type CallbackPacketData interface {
 	// GetSourceCallbackAddress should return the callback address of a packet data on the source chain.
 	// This may or may not be the sender of the packet. If no source callback address exists for the packet,