feat(index.js): export the layout helper so consumers can use layout.is('mobile') (#539)

affects: patternfly-react

This layout helper is used internally for the default stateful behavior of VerticalNav.
It would be
useful to expose for consumers who want to override parts of that state.

Author: mturley

packages/patternfly-react/src/index.js

@@ -46,4 +46,4 @@ export * from './components/TypeAheadSelect';
 export * from './components/UtilizationBar';
 export * from './components/Wizard';
 export * from './components/VerticalNav';
-export { patternfly } from './common/patternfly';
+export { patternfly, layout } from './common/patternfly';