Install system dependencies for ragg

ragg is a dependency of pkgdown, which is under Suggests.

Author: glin

.github/workflows/build.yaml

@@ -57,6 +57,7 @@ jobs:
           do
             eval sudo $cmd
           done < <(Rscript -e 'writeLines(remotes::system_requirements("ubuntu", "20.04"))')
+          sudo apt install -y libfontconfig1-dev libfribidi-dev libharfbuzz-dev libtiff-dev
 
       - name: Install dependencies
         run: |