Enable new typography scale

Author: DavidBiddle

app/frontend/entrypoints/application.scss

@@ -1,5 +1,6 @@
 $govuk-assets-path: "@govuk/assets/";
 $govuk-global-styles: true;
+$govuk-new-typography-scale: true;
 
 @import "pkg:govuk-frontend";
 @import "pkg:dfe-autocomplete";