Introduced a new `DocumentService.Client` project targeting `net462`, `net480`, and `net8.0`. The project includes metadata for NuGet packaging, such as `PackageId`, `Authors`, and `Company`, and references `Microsoft.Extensions.DependencyInjection` and `Microsoft.Extensions.Logging`.
Updated `DocumentService.sln` to include the new project, its build configurations, and solution folder associations.
Added `icon.png` as the NuGet package icon and included it in the project file.
