docs(plugins): Add example on how to tree shake locales from date-fns (#2524)

Add example on how to tree shake locales from date-fns.

Author: masives

src/content/plugins/context-replacement-plugin.md

@@ -3,9 +3,12 @@ title: ContextReplacementPlugin
 contributors:
   - simon04
   - byzyk
+  - masives
 related:
   - title: Issue 2783 - ContextReplacementPlugin Description
     url: https://github.com/webpack/webpack/issues/2783#issuecomment-234137265
+  - title: Using context replacement module for date-fns
+    url: https://github.com/date-fns/date-fns/blob/master/docs/webpack.md
 ---
 
 _Context_ refers to a [require with an expression](/guides/dependency-management/#require-with-expression) such as `require('./locale/' + name + '.json')`. When encountering such an expression, webpack infers the directory (`'./locale/'`) and a regular expression (`/^.*\.json$/`). Since the `name` is not known at compile time, webpack includes every file as module in the bundle.