Update README.md

Author: jbcaillau

README.md

@@ -16,7 +16,7 @@
 [release-url]: https://github.com/control-toolbox/OptimalControl.jl/releases
 
 The `OptimalControl.jl` package is the root package of the [control-toolbox ecosystem](https://github.com/control-toolbox).
-The control-toolbox ecosystem gathers `Julia` packages for mathematical control and applications. It aims to provide tools to modelise and solve optimal control problems by direct and indirect methods.
+The control-toolbox ecosystem gathers `Julia` packages for mathematical control and applications. It aims to provide tools to model and solve optimal control problems by direct and indirect methods.
 
 | **Documentation**  | **Code Status**  | **Release**  |
 |:-------------------|:-----------------|:-------------|