Discontinous content. Some media streams, like e.g. RTP streams received via UDP, have the characteristic, that some times packages are lost. This module provides a type that is isomorphic to Maybe to indicate that the content for a media frame is missing. It might take some effort to detect missing content, like a jitter buffer, or the comparison of sequence numbers.

TODO: Create a gap detection mechanism, a simple stateful monad that knows the next timestamp etc.