Add note about using local foreign-lib definitions

docs/0.8-upgrade.md

@@ -12,6 +12,32 @@ if you have direct dependencies to them.
 If you use additional React packages, you need to update Cljsjs packages
 for these to use new React foreign-lib name, `react` instead of `cljsjs.react`.
 **Subject to change, if this can be solved easily.**
+As a quick fix, you can add updated foreign-lib definition to your project,
+like following example for react-leaflet, and update your project
+to refer to the new name, and at the same time your can start using
+`:global-exports`:
+
+```cljs
+:foreign-libs [{:file "cljsjs/development/react-leaflet.inc.js"
+                :file-min "cljsjs/production/react-leaflet.min.inc.js"
+                :provides ["react-leaflet"]
+                :requires ["react"]
+                :global-exports {react-leaflet ReactLeaflet}}]}}
+```
+
+Old code:
+```cljs
+(ns ... (:require cljsjs.react-leaflet))
+
+(def Map (r/adapt-react-class js/ReactLeaflet.Map))
+```
+
+New code:
+```cljs
+(ns ... (:require [react-leaflet :as react-leaflet]))
+
+(def Map (r/adapt-react-class react-leaflet/Map))
+```
 
 ## Browser - node modules