[Prototype] Enable theme next for site component examples

[origami-z]

Adds a few theme next controls to component examples, just like mode and density

There should be some priorities for the new styling options (accent/corner/headingFont/actionFont) for the user to try out. My first thought is two font options is not high priority (also we don't have font file available on the site anyway)

Preview link : https://saltdesignsystem-git-3738-theme-next-site-examples-fed-team.vercel.app/salt/components/button/examples

• [ ] Decide which styling options toggle to show on the site
• [ ] Decide which control to use, switch / toggle button / anything else?
• [ ] Work on page responsiveness
• [ ] Should these options be persisted? should we use url param?

#3738