Fix deprecations #81
Description
I get the following deprecations when using this bundle:
User Deprecated: Method "Contao\ManagerPlugin\Bundle\BundlePluginInterface::getBundles()" might add "array" as a native return type declaration in the future. Do the same in implementation "MadeYourDay\RockSolidFrontendHelper\ContaoManagerPlugin" now to avoid errors or add an explicit return annotation to suppress this message.
User Deprecated: Method "Contao\ManagerPlugin\Routing\RoutingPluginInterface::getRouteCollection()" might add "?RouteCollection" as a native return type declaration in the future. Do the same in implementation "MadeYourDay\RockSolidFrontendHelper\ContaoManagerPlugin" now to avoid errors or add an explicit return annotation to suppress this message.
User Deprecated: Method "Symfony\Component\HttpKernel\Bundle\Bundle::build()" might add "void" as a native return type declaration in the future. Do the same in child class "MadeYourDay\RockSolidFrontendHelper\RockSolidFrontendHelperBundle" now to avoid errors or add an explicit @return annotation to suppress this message.