Adopt WebAPI only in ASP.NET Core

[liiamjones]

Given we have React in "adopt", I think we are adopting React for front end web, rather than the MVC (Views), Razor Pages or Blazor in ASP.NET Core. It's just the Web API part of ASP.NET Core we wish to "adopt"?

An interesting thread on slack talking about the proposal.

This PR splits out WebAPI, MVC Views, Blazor and Razor Pages into separate records, of which only WebAPI is "adopt", the others are "hold"

• [x] Are you happy for the content of this change to be publicly visible?
• [x] Are all new or updated entries marked as isNew = true?
• [x] Does radar.csv render correctly when viewed on Github?
• [x] Does the updated tech radar display as you expect?

[jcrang]

For what it's worth I think this is the direction Monitor is headed (see our guide on migrating to React here).

We're still a multi-page application with a bunch of Razor views and non-WebAPI controllers, but the views are getting smaller and the controller actions are being migrated to WebAPI.