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

Part-of: <https://gitlab.benkard.de/mulk/jgvariant/-/merge_requests/17>
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index aa2dc0b..d17de6e 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,9 +1,19 @@
+# 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:
-  - verify
-
+- verify
+- test
 image: maven:3-openjdk-17
-
 verify-job:
   stage: verify
   script:
-    - mvn verify
+  - mvn verify
+sast:
+  stage: test
+include:
+- template: Security/SAST.gitlab-ci.yml