usage for new UID matching docker

workflows/userdocker/instructions.md

+# docker setup
+rebuild the image with one final detail so as to 
+match the UID of the host and be able to share files
+w/o continuous premission trouble
+
+## build docker image
+
+`sudo docker build --build-arg USERID=$(id -u) -t rnaseqme --rm .`
+
+## start docker container
+
+Do this from the parent directory of the 'rnaseq-workshop' repository, so that the mounted folder contains the repository
+
+`sudo docker run -it --name rnalive --rm --mount type=bind,source="$(pwd)"/rnaseq-workshop,target=/home/zim-gast/rnaseq-workshop rnaseqme:latest`
+
+Or for course participants 
+`docker run -it --name rnalive --mount type=bind,source="$(pwd)"/rnaseq-workshop,target=/home/zim-gast/rnaseq-workshop rnaseqme:latest`
+