Fix link to example in readme.md (actix#1236)

* Fix link to example in readme.md

* Add links to openssl and rustls examples

* Rustls should be uppercase

README.md

@@ -68,7 +68,8 @@ async fn main() -> std::io::Result<()> {
   [Askama](https://github.com/actix/examples/tree/master/template_askama/) templates
 * [Diesel integration](https://github.com/actix/examples/tree/master/diesel/)
 * [r2d2](https://github.com/actix/examples/tree/master/r2d2/)
-* [SSL / HTTP/2.0](https://github.com/actix/examples/tree/master/tls/)
+* [OpenSSL](https://github.com/actix/examples/tree/master/openssl/)
+* [Rustls](https://github.com/actix/examples/tree/master/rustls/)
 * [Tcp/Websocket chat](https://github.com/actix/examples/tree/master/websocket-chat/)
 * [Json](https://github.com/actix/examples/tree/master/json/)