Configure SAST in `.gitlab-ci.yml`, creating this file if it does not already exist

.gitlab-ci.yml

+# You can override the included template(s) by including variable overrides
+# SAST customization: https://docs.gitlab.com/ee/user/application_security/sast/#customizing-the-sast-settings
+# Secret Detection customization: https://docs.gitlab.com/ee/user/application_security/secret_detection/#customizing-settings
+# Dependency Scanning customization: https://docs.gitlab.com/ee/user/application_security/dependency_scanning/#customizing-the-dependency-scanning-settings
+# Container Scanning customization: https://docs.gitlab.com/ee/user/application_security/container_scanning/#customizing-the-container-scanning-settings
+# Note that environment variables can be set in several places
+# See https://docs.gitlab.com/ee/ci/variables/#cicd-variable-precedence
+stages:
+- test
+sast:
+  stage: test
+include:
+- template: Security/SAST.gitlab-ci.yml