Fix react-leaflet example

docs/0.8-upgrade.md

@@ -21,10 +21,13 @@ to refer to the new name, and at the same time your can start using
 :foreign-libs [{:file "cljsjs/development/react-leaflet.inc.js"
                 :file-min "cljsjs/production/react-leaflet.min.inc.js"
                 :provides ["react-leaflet"]
-                :requires ["react"]
+                :requires ["react" "cljsjs.leaflet"]
                 :global-exports {react-leaflet ReactLeaflet}}]}}
 ```
 
+(Note: This still uses the old name for Leaflet, but you can also
+update Leaflet foreign-lib to use new name and `:global-exports`.)
+
 Old code:
 ```cljs
 (ns ... (:require cljsjs.react-leaflet))