install gnupg2 to vscode stage build (#27)

deployment/docker/Dockerfile

@@ -50,6 +50,7 @@ RUN groupadd --gid $USER_GID $USERNAME \
 # ********************************************************
 # * Anything else you want to do like clean up goes here *
 # ********************************************************
+RUN apt-get update && apt-get install -y gnupg2
 
 # [Optional] Set the default user. Omit if you want to keep the default as root.
 USER $USERNAME