[ci skip] Update README.md

Author: guilhermebodin

README.md

@@ -51,6 +51,7 @@ Current features include:
   * Unobserved components (local level, basic structural, ...)
   * SARIMA
   * Linear regression
+  * Naive models
 * Completion of missing values
 * Diagnostics for the residuals of fitted models
 * Visualization recipes
@@ -69,4 +70,4 @@ If you use StateSpaceModels.jl in your work, we kindly ask you to cite the [foll
       author={Raphael Saavedra and Guilherme Bodin and Mario Souto},
       journal={arXiv preprint arXiv:1908.01757},
       year={2019}
-    }
+    }