Provide an answer to a prompt, jumping to its reified continuation.
Unlike jump, this will not abort the current continuation, and the
reified computation will instead return its final result when finished.
Any effectful state of effects which have been run before the interpreter for
Shift will be embedded in the return value, and therefore the invocation
won't have any apparent effects unless these are interpreted in the final
monad.
Any higher-order actions will also not interact with the continuation in any
meaningful way; i.e. local or censor does
not affect it, catch will fail to catch any of its exceptions,
and listen will always return mempty.
The provided continuation may fail locally in its subcontinuations.
It may sometimes become necessary to handle such cases. To do so,
use 'reset'' together with release.