style(lib): run rustfmt and enforce in CI

examples/client_json.rs

@@ -4,8 +4,8 @@
 #[macro_use]
 extern crate serde_derive;
 
-use hyper::Client;
 use futures_util::StreamExt;
+use hyper::Client;
 
 // A simple type alias so as to DRY.
 type Result<T> = std::result::Result<T, Box<dyn std::error::Error + Send + Sync>>;