Create sample that detects whether the platform supports grpc-dotnet

A simple sample that includes code to detect wether the current platform supports grpc-dotnet.

Support requirements: https://learn.microsoft.com/en-us/aspnet/core/grpc/supported-platforms?view=aspnetcore-7.0

Code should look at the .NET version (.NET Core 3 or later) and optionally the OS (.NET Framework + WinHttpHandler scenario)

Start by reviewing the linked supported-platforms requirements and the repository's existing samples to identify the appropriate entry point. The sample is done when it checks for .NET Core 3 or later support and optionally handles the .NET Framework plus WinHttpHandler OS scenario.

Written by the indexing model from the issue text.