ReadAsync method does not filter errors into errors and warnings as the Read method does

[darrelmiller]

OpenAPI.NET/src/Microsoft.OpenApi.Readers/OpenApiYamlDocumentReader.cs

Lines 73 to 81 in 6ff3176

	var openApiErrors = document.Validate(_settings.RuleSet);
	foreach (var item in openApiErrors.Where(e => e is OpenApiValidatorError))
	{
	diagnostic.Errors.Add(item);
	}
	foreach (var item in openApiErrors.Where(e => e is OpenApiValidatorWarning))
	{
	diagnostic.Warnings.Add(item);
	}

Both Read and ReadAsync should separate Errors and Warnings.