fix: partial rebuild docker container

- optimise package dependency installation

Refs rvgest#1

Dockerfile

 FROM rocker/r-ver:4.0.3
 RUN apt-get update && apt-get install -y  git-core libcurl4-openssl-dev libgit2-dev libicu-dev libssl-dev libxml2-dev make pandoc pandoc-citeproc zlib1g-dev && rm -rf /var/lib/apt/lists/*
 RUN echo "options(repos = c(CRAN = 'https://cran.rstudio.com/'), download.file.method = 'libcurl')" >> /usr/local/lib/R/etc/Rprofile.site
-RUN R -e 'install.packages(c("config", "golem", "shiny", "processx", "attempt", "DT", "glue", "htmltools"))'
-RUN R -e 'install.packages(c("knitr", "rmarkdown"))'
-RUN R -e 'install.packages(c("jsonlite", "lubridate", "TSstudio"))'
+RUN R -e 'install.packages(c("golem", "processx", "DT", "shinydashboardPlus"))'
+RUN R -e 'install.packages(c("lubridate", "TSstudio"))'
 ARG COMMIT_HASH=unknown
 RUN R -e 'remotes::install_gitlab("in-wop/rvgest@master", host = "gitlab.irstea.fr")'
 RUN mkdir /build_zone