[wasm][framework] Add mono wasm framework libraries to build.

[kjpou1]

Incorporating libraries necessary to start using mono's HTTP handler and WebSocket interfaces.

Proposal for discussion.

[danroth27]

Fixes dotnet/aspnetcore#10489

[SteveSandersonMS]

Thanks for this, @kjpou1!

I took the approach here and included it in #1923. I changed the approach slightly in that it doesn't make sense to expose the framework libs as runtime references (i.e., in lib/netstandard1.0) because this package (Microsoft.AspNetCore.Blazor.Mono) isn't a runtime reference for apps anyway - it's only a build-time reference, so app developers still wouldn't obtain references to these packages. Longer term we should definitely look at making packages like WebAssembly.Bindings into published things that people can directly reference from their apps if they want.