BUGFIX: Prevent webpack from bundling react-ui-components twice

Some modules referred to the components via

```js
import { /* ... */  } from '@neos-project/react-ui-components';
```

This caused webpack to pull the components from
'@neos-project/react-ui-components/lib-esm' rather than
'@neos-project/react-ui-components/src', leading to the
component modules being bundled twice.

The solution was to add an alias for
'@neos-project/react-ui-components' to the root webpack
config, so that the components are always pulled from 'src/'
at build-time.

webpack.config.js

@@ -29,7 +29,10 @@ module.exports = merge(
             modules: [
                 path.resolve(__dirname, './packages/neos-ui/node_modules'),
                 path.resolve(__dirname, './node_modules')
-            ]
+            ],
+            alias: {
+                '@neos-project/react-ui-components$': path.resolve(__dirname, './packages/react-ui-components/src')
+            },
         },
         watchOptions: {
             ignored: /node_modules/