Update .gitlab-ci.yml file

.gitlab-ci.yml

@@ -7,6 +7,7 @@ building:
   stage: build
   script:
     - Rscript -e 'install.packages("remotes")'
+    - Rscript -e 'install.packages("devtools")'
     - R -e "remotes::install_deps(dependencies = TRUE)"
     - R -e 'devtools::check()'