First CTAN release of numodel-bundle (v0.2.0).

numodel-bundle is a LuaLaTeX package for writing and rendering
numerical models (Euler-integrated dynamical systems) directly
inside LaTeX documents, aimed at physics teaching material.

The bundle ships two modules:

* numodel      -- modelling engine: text-mode rule tables, Forrester
                  stock-and-flow diagrams (tight/forrester/edu styles),
                  numerical simulation in Lua, y(x)-plot integration.
* numodel-plot -- PGFPlots styling layer that auto-sizes plots to a
                  clean tick lattice; configurable axis-label formats
                  (IEEE, ISO 80000-1).

Pre-1.0 release; breaking changes still possible before 1.0.0.
