fix: add matchbox package to the docker image

without matchbox package the UI testing is not working as expected

.gitpod.Dockerfile

 FROM gitpod/workspace-full-vnc
 
+USER root
+
+RUN sudo apt-get update && sudo apt-get install -y matchbox && sudo apt-get clean && sudo rm -rf /var/cache/apt/* && sudo rm -rf /var/lib/apt/lists/* && sudo rm -rf /tmp/*
+
 USER gitpod
 
 RUN bash -c ". /home/gitpod/.sdkman/bin/sdkman-init.sh \