Add .NET Workflow SDK sections about DaprWorkflowClient and WorkflowContext usage #4956
Description
What content needs to be created or modified?
The DaprWorkflowClient usage shows information about lifecycle management and registration but not how to get an instance of the client.
How to: Author and manage Dapr Workflow in the .NET SDK points to the SDK example but does not show/explain Workflow SDK methods.
Describe the solution you'd like
Add code samples in the .NET SDK docs about the DaprWorkflowClient and the WorkflowContext.
Add links to examples in .NET SDK repo and Quickstarts/tutorials/workflow/csharp
Where should the new material be placed?
https://docs.dapr.io/developing-applications/sdks/dotnet/dotnet-workflow/dotnet-workflowclient-usage/
https://docs.dapr.io/developing-applications/sdks/dotnet/dotnet-workflow/dotnet-workflow-howto/
Code should be obtained from the SDK Workflow examples: https://github.com/dapr/dotnet-sdk/tree/master/examples/Workflow