add missing packages

.gitlab-ci.yml

 image: rocker/verse:4.0.0
 before_script:
   - R -e "install.packages('xaringanthemer')"
+  - R -e "install.packages('DiagrammeR')"
+  - R -e "install.packages('widgetframe')"
 pages:
   stage: deploy
   script:
   - Rscript -e "rmarkdown::render('presentation.Rmd', output_file = 'index.html')"
   - mkdir public
-  - cp index.html xaringan-themer.css public/
+  - cp index.html xaringan-themer.css mycss.css public/
   - cp -r index_files/ images/ public/
   artifacts:
     paths: