gRPC documentation and wizard

[bruno-garcia]

The gRPC code came in as a contribution, we merged and released.
We haven't added any docs for this yet.

Docs

There are docs on how to contribute to the docs. :)
But basically this is like the ASP.NET Core docs and goes under platforms/dotnet/guides.

Wizard

The wizard is a single file named after the platform (here it could be aspnetcore-grpc.md and goes in this folder:

https://github.com/getsentry/sentry-docs/tree/master/src/wizard/dotnet