Creates a 'promise' from an 'ncurlAio' object.
# S3 method for class 'ncurlAio'
as.promise(x)A 'promise' object.
This function is an S3 method for the generic as.promise for class
'ncurlAio'.
Requires the promises package.
Allows an 'ncurlAio' to be used with the promise pipe %...>%, which
schedules a function to run upon resolution of the Aio.