Make samples from documentation runnable via Telerik REPL

[egil]

Our friends from Telerik have been working on a prototype that will allow us to run bUnit tests inside their Blazor REPL environment. I suspect there will be some limitations here, like demos of WaitForX features and perhaps an injection of services, JSInterop, that won't work, but it may still be worthwhile to have this available in the remaining places.

Related issue: #145

Here is a demo:

1. Go to https://blazorrepl.telerik.com/GdkwlMbS11AjptTB51
2. The test is in the Test.cs file, the component under test is in the Counter.razor file
3. Click the RUN button to run the tests

The current suggestion is that the integration could work like this:

1. During deployment/build of the docs site, each "sample test/component-under-test pair" is uploaded to the Blazor REPL via a command line tool.
2. Somewhere next to each sample in the docs we add a link that points to related sample
3. If the user clicks the link, a new window is opened and they can play around with the code

Here are the "upload samples" details:

Auth
HeaderKey: "API-KEY"
API KEY value: "REPL_API_KEY (in github secrets)"
Http Verb: POST
Content-Type: application/json
Url: https://test.snippets.blazorrepl.telerik.com/
Body Schema: { files: [{ path: '', content: '' }], installedPackages: [{ name: '', version: '' }] }

The file which is first in the files array will appear first in the REPL and it will be the default visible file.

If everything is ok, the API will return 200 OK with the snippet ID

Next step

1. Figure out which samples make sense to use the REPL with
2. Figure out a good way to integrate this with our docs build pipeline