doc: getting started for external dependency (#2752)

README.md

@@ -48,6 +48,19 @@ CtClass l = Launcher.parseClass("class A { void m() { System.out.println(\"yeah\
 
 Some examples about the usage of Spoon can be found on [spoon-examples](https://github.com/SpoonLabs/spoon-examples).
 
+:warning: We introduced in Spoon 7.1.0 an external dependency that is not available on Maven Central. 
+In order to use it properly, please add also the following repository in your pom:
+
+```
+<repositories>
+<repository>
+      <id>inria</id>
+      <name>triskell-public-release</name>
+      <url>http://maven.inria.fr/artifactory/triskell-public-release</url>
+</repository>
+</repositories>
+```
+
 
 ## Contributing in 2 seconds