Add extra dependencies for the tests

Author: andreaTP

exercise/pom.xml

@@ -27,6 +27,16 @@
       <version>3.15.0</version>
       <scope>test</scope>
     </dependency>
+    <dependency><!-- Used here: https://github.com/exercism/java/blob/acfdd2b654a1e2b8bb497c3af25a9e2eff1044e0/exercises/practice/rest-api/build.gradle#L14 -->
+      <groupId>org.json</groupId>
+      <artifactId>json</artifactId>
+      <version>20190722</version>
+    </dependency>
+    <dependency><!-- Used here: https://github.com/exercism/java/blob/acfdd2b654a1e2b8bb497c3af25a9e2eff1044e0/exercises/practice/hangman/build.gradle#L14 -->
+      <groupId>io.reactivex.rxjava2</groupId>
+      <artifactId>rxjava</artifactId>
+      <version>2.2.12</version>
+    </dependency>
   </dependencies>
 
   <build>