added support for docker to run with a certain PUID and PGID

Dockerfile

@@ -1,6 +1,6 @@
 FROM node:8-alpine
 
-RUN apk add yarn git bash
+RUN apk add yarn git bash s6
 RUN mkdir -p /opt/mykb
 
 # install node_modules to tmp so it can be cached
@@ -15,13 +15,13 @@ RUN cd /opt/mykb && yarn build
 COPY docker_startup.sh /mykb
 RUN chmod +x /mykb
 
-VOLUME /kb
-VOLUME /db
-VOLUME /config
+VOLUME /kb /db /config
 
 EXPOSE 3030
 
 ARG GIT_NAME=mykb
 ARG GIT_EMAIL=mykb@localhost
+ARG PUID
+ARG PGID
 
 CMD [ "/mykb" ]