Run ShellCheck against script in CI

.editorconfig

@@ -9,3 +9,6 @@ indent_size = 4
 charset = utf-8
 trim_trailing_whitespace = true
 insert_final_newline = true
+
+[*.{yaml,yml}]
+indent_size = 2

.github/workflows/tests.yml

@@ -0,0 +1,21 @@
+---
+name: Tests
+
+on:
+  push: ~
+  pull_request: ~
+
+permissions:
+  contents: read
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Run ShellCheck
+        uses: ludeeus/action-shellcheck@master
+        with:
+          severity: style