Refactor exception to a more descriptive one

Taking as a proxy the file Http.java file in the same directory, we have replaced the RuntimeException class for an IllegalStateException containing a descriptive message.

Author: guillemsarda

sonar-plugin/bridge/src/main/java/org/sonar/plugins/javascript/bridge/BridgeServerImpl.java

@@ -259,7 +259,7 @@ void establishWebSocketConnection() {
       this.client.connectBlocking();
     } catch (InterruptedException e) {
       Thread.currentThread().interrupt();
-      throw new RuntimeException(e);
+      throw new IllegalStateException("WebSocket connection interrupted", e);
     }
   }