WIP: Initial draft of spec

Closes #4 (closed)

This PR adds a high-level specification, which should refine the theoretical framework we're employing for the into a user interface for the intervention.

More extensive details regarding the methodology employed for this specification can be found in Goguen's paper on algebraic specification linked in #4 (closed). But I aim to add a short right as part of this MR with documentation on how the specification is derived and on how to read it.