Add dependency for asiatics font

Dockerfile

@@ -1,4 +1,8 @@
 FROM jetty
 MAINTAINER D.Ducatel
 
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends graphviz fonts-wqy-zenhei && \
+    rm -rf /var/lib/apt/lists/*
+
 ADD target/plantuml.war /var/lib/jetty/webapps/ROOT.war