Add example of shutting down connection manager to documentation

Author: dakrone

Readme.md

@@ -558,6 +558,10 @@ for each request:
 (get "http://aoeu.com/1" {:connection-manager cm2})
 (post "http://aoeu.com/2" {:connection-manager cm})
 (get "http://aoeu.com/3" {:connection-manager cm2})
+
+;; Don't forget to shut it down when you're done!
+(clj-http.conn-mgr/shutdown-manager cm)
+(clj-http.conn-mgr/shutdown-manager cm2)
 ```
 
 See the docstring on `make-reusable-conn-manager` for options and

changelog.org

@@ -8,7 +8,7 @@
 #+LANGUAGE: en
 
 * Changelog
-  List of user-visible changes that have gone into each release
+List of user-visible changes that have gone into each release
 ** 0.9.0
 - Bumped httpcore to 4.3.2
 - Merged https://github.com/dakrone/clj-http/pull/190 to support file multiparts