corrections de coquilles sur les liens

readme_en.md

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 Road2 is a route and isochrone calculation server written in Javascript and designed to work with NodeJS. This server offers the calculation of routes and isochrones via existing engines like [OSRM](https://github.com/Project-OSRM/osrm-backend) or [PGRouting](https://pgrouting.org/ ). Road2 is therefore an interface for calculation engines. These are not done in Road2's code but via calls to its engines. This can mean calling a library, or a database, or another web service.
 
-Road2 was designed with the idea of being able to easily add new engines and new APIs, and this, in a completely transparent way for each other. In other words, adding an engine has no impact on existing APIs. The goal is to facilitate the addition of new features while maintaining access to the service. For a longer discussion on the software concepts introduced in Road2, please refer to the [following] documentation (./documentation_en/developers/concepts.md).
+Road2 was designed with the idea of being able to easily add new engines and new APIs, and this, in a completely transparent way for each other. In other words, adding an engine has no impact on existing APIs. The goal is to facilitate the addition of new features while maintaining access to the service. For a longer discussion on the software concepts introduced in Road2, please refer to the [following documentation](./documentation_en/developers/concepts.md).
 
 Currently, Road2 offers three engines, OSRM, PGRouting and Valhalla, through a single REST API.