Document relevant Blazor topics

[Tarmil]

We should expand the documentation to cover aspects of Blazor that are relevant to Bolero. In no particular order:

• Dependency injection using [<Inject>].
• JS interop using IJSRuntime, including the JSRuntime property provided by ProgramComponent, as well as how to use it with Elmish commands.
• Ajax calls using HttpClient, including how to use it with Elmish commands.
• Server-side Blazor, including how it interacts with Remoting and HTML hot reloading.