Surface DCR For Apps Articles In Preview

Make DCR for apps articles available in preview. In the long term we probably want some UI changes to viewer so that anyone can view an apps article alongside the dotcom version. In the short term we may just be able to make the apps query param available in preview/viewer so that interactives developers can test their content.

## Background

At the moment there's no way to see the apps version of a DCR article in preview. Generally speaking the dotcom and apps versions of a DCR article should be very similar, so viewing the dotcom version may be enough for most article formats for now.

However, the customisation that occurs on interactive articles can sometimes clash with the few differences that do exist between dotcom and apps articles, and currently there's no way for interactives developers (e.g. the Editorial Design team) to preview their changes on apps articles to mitigate these clashes.

We've filtered out interactives from the DCR rollout on apps for now: https://github.com/guardian/mobile-apps-api/pull/2822

https://viewer.gutools.co.uk/proxy/preview/info/2023/oct/24/standardisation-the-merit-of-consistent-patterns?dcr=apps#noads
https://viewer.gutools.co.uk/preview/business/2023/nov/23/openai-was-working-on-advanced-model-so-powerful-it-alarmed-staff?dcr=apps