docs: add clone docs for strategy (closes #520)

src/client/stripe.rs

@@ -59,6 +59,16 @@ impl Client {
     }
 
     /// Set the request strategy for the client.
+    ///
+    /// Note: the client is cheap to clone so if you require a new client
+    ///       temporarily with a new strategy you can simply clone it
+    ///       and keep going.
+    ///
+    /// ```no_run
+    /// let idempotent_client = client
+    ///     .clone()
+    ///     .with_strategy(RequestStrategy::Idempotent("my-key".to_string()));
+    /// ```
     pub fn with_strategy(mut self, strategy: RequestStrategy) -> Self {
         self.strategy = strategy;
         self