Update FiltersSample to ASP․NET Core 3.1

[doggy8088]

Update FiltersSample to ASP․NET Core 3.1

[guardrex]

Hello @doggy8088 ... We must maintain the 2.x sample, which is still supported. Updates like this require changes to the folder structure (when a 3.x sample doesn't exist for a topic) and text changes to the topic to cross-link the 2.x and 3.x samples into the text. If you want to handle the update, that's certainly welcome. See this answer that I provided for more info on how these are set up for 2.x and 3.x 👉 #15924 (comment)

You can also look at some of the existing topics and samples that have the sample versioning pattern in place. For example ...

• Configuration
  • https://github.com/aspnet/AspNetCore.Docs/edit/master/aspnetcore/fundamentals/configuration/index.md
  • https://github.com/aspnet/AspNetCore.Docs/tree/master/aspnetcore/fundamentals/configuration/index/samples
• DI
  • https://github.com/aspnet/AspNetCore.Docs/edit/master/aspnetcore/fundamentals/dependency-injection.md
  • https://github.com/aspnet/AspNetCore.Docs/tree/master/aspnetcore/fundamentals/dependency-injection/samples

If you want to take it on, then let's discuss it on the sample tracking issue: Please feel free to ask me questions there 👉 #5495