ci: test shell files with shellcheck

Change-Id: If32fcb000afd8cc1112123a3f7e069bb408a05cd

.github/workflows/check.yml

@@ -0,0 +1,16 @@
+name: check
+
+on:
+  push:
+    branches [ main ]
+  pull_request:
+    branches: [ "*" ]
+  workflow_dispatch:
+
+jobs:
+  shellcheck:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - run: shellcheck *.sh
+