No way to specify some Availability API request parameters using builder

[adionne-cc]

I was going about using this library to form and send requests to the Availability API using

cronofy-csharp/src/Cronofy/CronofyAccountClient.cs

Line 495 in 2673f54

public IEnumerable<AvailablePeriod> GetAvailability(AvailabilityRequest availabilityRequest)

I noticed however that there are some missing request parameters that the Availability API does accept in actual requests including:

• response_format
• max_results

I would like to see these added to the library. I can add them myself and put up a PR if that route makes sense. Thanks!