Updates example commands to include async features

Due to the error: "target `XXX` in package `async-tungstenite`
requires the features: `async-std-runtime`".

Also updated the echo-server example command to start echo-server
instead of server.

examples/echo-server.rs

@@ -2,11 +2,11 @@
 //!
 //! You can test this out by running:
 //!
-//!     cargo run --example server 127.0.0.1:12345
+//!     cargo run --features="async-std-runtime" --example echo-server 127.0.0.1:12345
 //!
 //! And then in another window run:
 //!
-//!     cargo run --example client ws://127.0.0.1:12345/
+//!     cargo run --features="async-std-runtime" --example client ws://127.0.0.1:12345/
 
 use std::{env, io::Error};
 

examples/server.rs

@@ -6,11 +6,11 @@
 //!
 //! You can test this out by running:
 //!
-//!     cargo run --example server 127.0.0.1:12345
+//!     cargo run --features="async-std-runtime" --example server 127.0.0.1:12345
 //!
 //! And then in another window run:
 //!
-//!     cargo run --example client ws://127.0.0.1:12345/
+//!     cargo run --features="async-std-runtime" --example client ws://127.0.0.1:12345/
 //!
 //! You can run the second command in multiple windows and then chat between the
 //! two, seeing the messages from the other client as they're received. For all