ci(lint): add shell linter - Differential ShellCheck

It performs differential ShellCheck scans and report results directly in pull request.

documentation: https://github.com/redhat-plumbers-in-action/differential-shellcheck

Co-authored-by: David Rheinsberg <david.rheinsberg@gmail.com>

.github/workflows/differential-shellcheck.yml

@@ -0,0 +1,24 @@
+name: "Differential ShellCheck"
+on:
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  lint:
+    name: "Differential Shell Check"
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: "Clone Repository"
+      uses: actions/checkout@v3
+      with:
+        fetch-depth: 0
+
+    - name: "Differential ShellCheck"
+      uses: redhat-plumbers-in-action/differential-shellcheck@v3
+      with:
+        severity: warning
+        token: ${{ secrets.GITHUB_TOKEN }}