Razor code snippets break doc builds about highlight.js

[guardrex]

I think I've narrowed this down to snippets.

Cross-links without a snippet work 👍 ...

[!code-razor[](samples/SampleApp/Pages/RouteParameter.razor?highlight=1)]

In-text code is fine 👍 ...

```razor
@page "/my-cool-page"

<h1>Cool Blazor Page</h1>
`​`​`

The problem seems to be when using a snippet 💥😢 ...

[!code-razor[](samples/SampleApp/Pages/RouteParameter.razor?name=snippet1&highlight=1)]

... where snippet1 is composed in the file as ...

<!-- <snippet1> -->
@page "/my-cool-page"

<h1>Cool Blazor Page</h1>
<!-- </snippet1> -->

@code {
    ...
}

That approach works if the code language is cshtml (code-cshtml), but switching to razor (code-razor) yields the error ...

razor is not supported languaging name, alias or extension for parsing code snippet with tag name, you can use line numbers instead

My workaround will be to place snippets into the doc markdown files until this is resolved. Having chstml appear on our examples in the Blazor docs is confusing our readers, so I feel that it's important to workaround the issue for now.