Provide a simple way to disable interactive UI elements during prerendering and then enable them once interactivity is ready

There is often a delay in Blazor apps between when an UI element is shown to the user and when it is actually interactive. For example, you prerender the Counter button, but it doesn't respond to button clicks until the WebAssembly runtime is up and running.

We should of course continue to find ways to optimize Blazor so this delay is as minimal as possible, ideally unnoticeable. But currently users often need to build a UI experience themselves that disables UI elements and then enables them once interactivity is available.

We should consider how we might make this UX pattern easier. Maybe the framework could provide a sensible default experience that users can then customize?