Link to app sample

### Description

This issue was filed through the unified customer feedback tool.

Customer Verbatim:
"Would be nice to have a link to a github page so that you can just download the code (git clone) and start play around with it - some people find it easier to learn that way :)"

### Page URL

https://learn.microsoft.com/en-us/aspnet/core/grpc/?view=aspnetcore-8.0

### Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/grpc/index.md

### Document ID

048d1977-93aa-f28a-60ec-6806dec3f70a

### Article author

@JamesNK