Add : CI/CD pipeline for latex

resolves #31 (closed) Adds a file to run CI/CD pipeline for latex and store the pdf report as artifacts,anytime a new change is made

.gitlab-ci.yml

+compile_pdf:
+  stage: build
+  image: registry.gitlab.com/islandoftex/images/texlive:latest  # Docker image for LaTeX from https://hub.docker.com/
+  script: 
+    - lualatex main.tex # building the pdf
+    - biber main
+    - lualatex main.tex
+  after_script: cat main.log
+  artifacts:
+    paths: 
+      - main.pdf  # instructing GitLab to keep the main.pdf file