Fix up dockerfile in containerization chapter

[chendaniely]

• https://ubc-dsci.github.io/reproducible-and-trustworthy-workflows-for-data-science/materials/lectures/05-containerization.html

current Dockerfile example I showed in class was this:

FROM rocker/rstudio

WORKDIR /home/rstudio

# you can use remotes::install_version() as well instead of using renv

COPY --chown=rstudio:rstudio renv.lock .
COPY --chown=rstudio:rstudio renv renv
COPY --chown=rstudio:rstudio .Rprofile .

RUN ls -alh

USER rstudio
RUN Rscript -e "renv::repair()"
USER root

The USER swapping seems really hacky, as well as the chown bits.
It does mean we have to talk + review more of whoami and ls -alh commands, but there might be a simpler way to fully setup the container instead of this way.

I think the previous class was using conda mainly so this wasn't a problem.