Consider documenting the gRPC client APIs

[rmfaheem]

In the legacy docs, we had a complete documentation of the API of the legacy dotnet client. This type of documentation is immensely helpful to people who are just getting started with ESDB. We could consider adding this to the current docs as well.

[alexeyzimarev]

The old docs were generated by DocFX, which can only do it for .NET. It also doesn't produce Markdown files by default, and those files it manages to produce often break the generator as "it wasn't designed to generate Markdown" (from a discussion in docfx repo). Each other language requires its own tooling to generate code API docs. It's quite a lot of work, I am not sure when we can do that. Although I agree it is useful.