add shellcheck github workflow

Author: ncopa

.github/workflows/test.yaml

@@ -1,6 +1,14 @@
 name: test
 on: [push]
 jobs:
+  lint:
+    name: shellcheck
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Run Shellcheck
+        uses: ludeeus/action-shellcheck@master
 
   alpine:
     runs-on: ubuntu-latest