add make lesson-check-all step

Author: zkamvar

.github/workflows/template.yml

@@ -150,4 +150,5 @@ jobs:
           done < <(Rscript -e 'cat(remotes::system_requirements("ubuntu", "20.04"), sep = "\n")')
 
       - run: make site
+      - run: make lesson-check-all
         working-directory: lesson