Configure the Blazor WASM runtime

[guardrex]

Fixes #30320

Confirm what I called these in case I'm making up my own 🦖 Blazor framework .... again! 😆

To configure the .NET WebAssembly runtime, use the configureRuntime function with the dotnet runtime host builder.

❓ ... dotnet ... the "runtime host builder"?

UPDATE: On this PR, I had configureRuntime property. I've updated that to "function" on a different PR.

@maraf ... I took your test example for the doc coverage. If either you or Pavel have something better for the example, I'm 👂.

Finally, this is used to configure quite a few runtime-y things. I see what looks like an incomplete list at ...

dotnet/aspnetcore#49264 (comment)

What do we want to say about that (or cross-link for it)?

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Internal previews

📄 File	🔗 Preview link
aspnetcore/blazor/fundamentals/startup.md	ASP.NET Core Blazor startup
aspnetcore/release-notes/aspnetcore-8.0.md	What's new in ASP.NET Core 8.0

[guardrex]

I'm going to go ahead and merge because we can't hold up the release notes topic at this time. We're on a HIGH doc churn day with RC1 🏃🏃🏃🏃😰.

I'll patch any updates into the text/example that you see fit. Please leave your comments here.

[maraf]

@guardrex I think the same is good enough. I should also show the other part, eg

Blazor.runtime.getAssemblyExports(...);

The Blazor.runtime gives access to Runtime API of running .NET https://github.com/dotnet/aspnetcore/blob/cdbb59f6a7ee4cc2a7727a4555c53f4578a89276/src/Components/Web.JS/src/GlobalExports.ts#L42, returned type is https://github.com/dotnet/aspnetcore/blob/cdbb59f6a7ee4cc2a7727a4555c53f4578a89276/src/Components/Web.JS/%40types/dotnet/dotnet.d.ts#L343-L384

[guardrex]

I added it after this PR on #30339 ...

The .NET runtime instance can be accessed from Blazor.runtime.

Live topic section ...

https://learn.microsoft.com/en-us/aspnet/core/blazor/fundamentals/startup?view=aspnetcore-8.0#configure-the-net-webassembly-runtime