Add settings and notification center to docs

[MarvinKlein1508]

Vincent Baaij (@vnbaaij) you wanted to add the settings and notification panels from the v4 docs to the v5 docs to give users an idea on how they can built this on their own.

[dvoituron]

I don’t think this button is necessary. We already have a Dark/Light button and an LTR button.
The only thing left would be the colour change, which is already explained on the page https://v5.fluentui-blazor.net/Theme/Designer

[MarvinKlein1508]

Denis Voituron (@dvoituron) it's not about the features itself. It's about grouping them into a panel which the user can access from the top of the page. I quite like the flyout and it allows us to add more toggles in the future :)

[vnbaaij]

And I think it is a good showcase/example on how sich functionality could/should be created