[docs] Create /examples folder

[oliviertassinari]

Summary

This is about introducing an /examples folder like Material UI, Next.js.

Motivation

Those examples would have two separate purposes:

• Demonstrate ready-to-use integrations. e.g. with the Link of Next.js, with the modifier of Tailwind CSS, etc. This support guide docs pages.
• Have a standard project that developers can use to report complex problems that they can't reproduce with CodeSandbox or StackBlitz. This saves time for engineers to get it up and running faster. This is a regression from MUI Base. We are missing clear support instructions https://mui.com/base-ui/getting-started/support/#bug-reproductions.