Adding example of AntiForgery scenarios with standards Web APIs

[brunolins16]

Part of dotnet/aspnetcore#42586

Was decided to not have any in-box default behavior for both (API controllers and Minimal APIs), however, we should add an example of how the users could implement it using IAntiforgery services.

Here is a sample code with the server implementation: https://gist.github.com/brunolins16/3d11b2fd9861afaec22e79abfc2a55fd

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Document Details

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• ID: 47b14f57-82ac-a2e2-cbc7-22a81a60f4ac
• Version Independent ID: bffca13c-223f-c61f-9cb2-9da8811eecfa
• Content: Prevent Cross-Site Request Forgery (XSRF/CSRF) attacks in ASP.NET Core
• Content Source: aspnetcore/security/anti-request-forgery.md
• Product: aspnet-core
• Technology: aspnetcore-security
• GitHub Login: @Rick-Anderson
• Microsoft Alias: riande

[brunolins16]

@Rick-Anderson I will create a PR for this issue and ask for your review, ok?

[Rick-Anderson]

@brunolins16 don't worry about the wording, I can clean that up. Just get a good start.