Merge branch 'feature/cicd' into 'master'

Creation of CI/CD

See merge request physics/electric-field!8

.gitlab-ci.yml

+image: gcc
+
+stages:
+  - build
+
+before_script:
+  - make clean
+
+build:
+  stage: build
+  script:
+    - make
+  only:
+    - master
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