Merge branch 'www-gitlab-com-yamllint' into 'master'

Add yamllint to the www-gitlab-com image

See merge request gitlab-org/gitlab-build-images!294

scripts/install-www-gitlab-com

@@ -11,6 +11,7 @@ apt-get install -yq --no-install-recommends \
   make gcc g++ locales \
   rsync git-core texlive-latex-recommended texlive-xetex \
   texlive-fonts-recommended lmodern ed file curl gnupg2 \
+  yamllint python3-pkg-resources \
 
 cd /tmp
 curl -L -O https://github.com/jgm/pandoc/releases/download/2.3.1/pandoc-2.3.1-linux.tar.gz