text: Title: Add a tabbed navigation to move between `vizro-core` and `vizro-ai` docs
  Body: The Kedro docs (https://docs.kedro.org) has a tabbed navigation.
  
  <img width="1089" alt="image" src="https://github.com/mckinsey/vizro/assets/5180475/5527861a-aba0-45d8-8d36-977226c098f8">
  
  
  Why can't we have something similar? This shouldn't be a major piece of work and will simply enable users to move between https://vizro.readthedocs.io/en/stable/ and https://vizro.readthedocs.io/projects/vizro-ai/en/latest/ at a top level.
  
  We did this in Kedro in the `layout.html` https://github.com/kedro-org/kedro/blob/main/docs/source/_templates/layout.html
  
  Anyone better at front end design and development will be able to add to this ticket to explain how to make it work.
  
  Ideally we should have some design input but I know we are already waiting on that for other tickets so perhaps we could mock this up in code and then add it to the queries we have for Design.
  
  Suitable for help from anyone with front-end skills, no prior knowledge of Vizro is required, so I'm marking as "Help Wanted" and "Good First Issue"