Make it clear how to run all examples (#92)

* Handle errors in websocket example

* Make it clear how to run all examples

examples/versioning.rs

@@ -1,3 +1,9 @@
+//! Run with
+//!
+//! ```not_rust
+//! cargo run --example versioning
+//! ```
+
 use axum::response::IntoResponse;
 use axum::{
     async_trait,