Add Shell linter - Differential-ShellCheck (#1419)

Signed-off-by: Jan Macku <jamacku@redhat.com>
Co-authored-by: Mislav Marohnić <git@mislav.net>

.github/workflows/lint.yml

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