Add shellcheck to CI

.gitlab-ci.yml

@@ -29,6 +29,11 @@ ruff:
   stage: lint
   script: poetry run ruff check *.py tests/
 
+shellcheck:
+  image: koalaman/shellcheck-alpine:latest
+  stage: lint
+  script: shellcheck init.sh
+
 pytest:
   stage: test
   script: