docs(readme): add caution note about repository archiving (#501)

Added caution note about archiving the Arcus Web API repository and suggested Microsoft alternatives.

Author: stijnmoreels

README.md

@@ -1,3 +1,9 @@
+> [!CAUTION]
+> Arcus Web API repository is being archived, please consider the following built-in Microsoft alternatives:
+> * [HTTP request logging](https://learn.microsoft.com/en-us/aspnet/core/fundamentals/http-logging/)
+> * [Exception handling middleware](https://learn.microsoft.com/en-us/aspnet/core/fundamentals/error-handling)
+> * [Certificate authentication](https://learn.microsoft.com/en-us/azure/api-management/api-management-howto-mutual-certificates-for-clients)
+
 # Arcus - Web API
 [![Build Status](https://dev.azure.com/codit/Arcus/_apis/build/status/Commit%20builds/CI%20-%20Arcus.WebApi?branchName=main)](https://dev.azure.com/codit/Arcus/_build/latest?definitionId=733&branchName=main)
 [![NuGet Badge](https://buildstats.info/nuget/Arcus.WebApi.Security?includePreReleases=true)](https://www.nuget.org/packages/Arcus.WebApi.Security/)