ci: Run shellcheck validation on push.

Author: webbju

.github/workflows/build.yml

@@ -0,0 +1,15 @@
+name: Build
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  shellcheck:
+    name: Shellcheck
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ludeeus/action-shellcheck@master