add latex template

latex.gitlab-ci.yml

+# Required
+## SOURCE
+.build_pdf:
+  tags:
+    - amd64  # texlive image doesn't support arm64
+  image: registry.gitlab.com/islandoftex/images/texlive:latest
+  script:
+    - latexmk -outdir=../out -cd -interaction=batchmode -pdf $SOURCE
+  artifacts:
+    paths:
+      - out/*.pdf