workflows: Add required shellcheck workflow

Start with a required smaller set of shellchecks
to try and prevent regressions whilst we fix
the current problems

Signed-off-by: stevenhorsman <steven@uk.ibm.com>

.github/workflows/shellcheck_required.yaml

@@ -0,0 +1,32 @@
+
+# https://github.com/marketplace/actions/shellcheck
+name: Shellcheck required
+
+on:
+  workflow_dispatch:
+  pull_request:
+    types:
+      - opened
+      - edited
+      - reopened
+      - synchronize
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  shellcheck:
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout the code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - uses: actions/checkout@v4
+      - name: Run ShellCheck
+        uses: ludeeus/action-shellcheck@master
+        with:
+          severity: error
+          ignore_paths: ./src/runtime/vendor/**