Create sample for updating or signaling the Workflow state

We need to bring example in documentation of how to updating the and/or signaling and/or querying states of any variable states in workflow

// Update state of workflow.
`Task UpdateWorkflowParams(GreetingParams greetingParams) => _currentParams = greetingParams;`

// Update state of workflow.
`Task CompleteWorkflow() => _complete = true;`
then
`Workflow.WaitCondition(() => _complete == true);` triggered

// Query state in Workflow
`string GetValueOfName() => _name;`