Read custom header to generate webp format

Helpers.cs

public virtual string GetSupportedFormats(HttpContextBase context)
{
	var acceptTypes = context?.Request?.AcceptTypes ?? new string[] { };
	if (acceptTypes.Any())
	{
		return PipelineHelpers.RunDianogaGetSupportedFormatsPipeline(acceptTypes);
	}

	var customAccept = context?.Request?.Headers?["customAccept"];
	if (!string.IsNullOrEmpty(customAccept))
		return PipelineHelpers.RunDianogaGetSupportedFormatsPipeline(new string[] { customAccept });

	return string.Empty;
}

public virtual bool CheckSupportedFormat(HttpContextBase context, string extension)
{
	var acceptTypes = context?.Request?.AcceptTypes ?? new string[] { };
	if (acceptTypes.Any())
		return CheckSupportedFormat(string.Join(",", acceptTypes), extension);

	var customAccept = context?.Request?.Headers?["customAccept"];
	if (!string.IsNullOrEmpty(customAccept))
		return CheckSupportedFormat(customAccept, extension);

	return false;
}