readme: added gray-scott example

Author: jviquerat

README.md

@@ -53,4 +53,5 @@ spk --train <json_file>
 | `heat-source` | 14                | Optimizing the positions of heat sources to obtain a high temperature distribution with low variance in a target area (solved with `CMAES`)                                                                                                                | <img width="300" alt="gif" src="sparkle/msc/heat_source_cmaes.gif"> |
 | `packing`     | 26                | Finding the best disk packing within a square domain, adapted from <a href="https://erich-friedman.github.io/packing/index.html">this ref</a> (solved with `PBO`)                                                                                          | <img width="300" alt="gif" src="sparkle/msc/packing_pbo.gif">       |
 | `emstack`     | 40                | Optimizing the reflectance of a dielectric mirror with mixed continuous/discrete variables (solved with `PBO`)                                                                                                                                             | <img width="300" alt="gif" src="sparkle/msc/emstack_pbo.gif">       |
+| `gray-scott`  | 2                 | Maximizing the curvature of the final pattern by controlling the feed and kill rates of the chemical species (solved with `EGO`)                                                                                                        | <img width="300" alt="gif" src="sparkle/msc/gray_scott_ego.gif">    |