Added lint job to CI

.gitlab-ci.yml

@@ -7,6 +7,16 @@ stages:
 variables:
   TOOLNAME: ripgrep
   REPOURL: https://gitlab.com/wt0f/asdf-ripgrep.git
+  SHELLCHECK_VERSION: stable
+
+asdf-plugin-lint:
+  stage: lint
+  before_script:
+    - apt update && apt install -y xz-utils wget
+    - wget -qO- https://github.com/koalaman/shellcheck/releases/download/$SHELLCHECK_VERSION/shellcheck-$SHELLCHECK_VERSION.linux.x86_64.tar.xz | tar xJv
+    - cp shellcheck-$SHELLCHECK_VERSION/shellcheck /usr/bin
+  script:
+    - shellcheck -x bin/* -P lib/
 
 asdf-plugin-test:
   stage: test