docs(guides): replace [contenthash] with [chunkhash] (#1477)

Author: guillaumevincent

content/guides/caching.md

@@ -105,7 +105,7 @@ __webpack.config.js__
 +     })
     ],
     output: {
-      filename: '[name].[contenthash].js',
+      filename: '[name].[chunkhash].js',
       path: path.resolve(__dirname, 'dist')
     }
   };