Test data for turing-surface, to be used as a sibling repository.

Reference solutions for validating reaction-diffusion solvers on curved
surfaces, so independently-written solvers can be checked against each
other. Each case below documents the simulation being solved and the data
format its reference file(s) use.

## Cases

- [`cases/schnakenberg-ellipsoid.md`](cases/schnakenberg-ellipsoid.md) —
  Schnakenberg reaction-diffusion on a triaxial ellipsoid.