Fix another broken README link (#8)

* Fix another broken README link

* Make demo into a link

README.md

@@ -43,7 +43,7 @@ func withCORS(connectHandler http.Handler) http.Handler {
 ## Ecosystem
 
 * [connect-go]: the Go implementation of Connect's RPC runtime
-* [examples-go]: service powering demo.connectrpc.com, including bidi streaming
+* [examples-go]: service powering [demo.connectrpc.com][demo], including bidi streaming
 * [grpchealth]: gRPC-compatible health checks
 * [grpcreflect]: gRPC-compatible server reflection
 * [authn]: pluggable authentication for Connect servers
@@ -67,11 +67,13 @@ make breaking changes in the 1.x series of releases.
 Offered under the [Apache 2 license][license].
 
 [Getting Started]: https://connectrpc.com/docs/go/getting-started
+[authn]: https://github.com/connectrpc/authn-go
 [blog]: https://buf.build/blog/connect-a-better-grpc
 [conformance]: https://github.com/connectrpc/conformance
 [connect-es]: https://github.com/connectrpc/connect-es
 [connect-go]: https://github.com/connectrpc/connect-go
 [cors]: https://github.com/connectrpc/cors-go
+[demo]: https://demo.connectrpc.com
 [docs]: https://connectrpc.com
 [examples-go]: https://github.com/connectrpc/examples-go
 [go-support-policy]: https://golang.org/doc/devel/release#policy