ci: add workflow to validate schema

.github/workflows/check-schema-policy-controller.yml

@@ -0,0 +1,41 @@
+name: Check Helm Schema (policy-controller only)
+
+on:
+  pull_request:
+    paths:
+      - "charts/policy-controller/**"
+
+jobs:
+  schema:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+
+      - name: setup go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '>=1.23.1'
+
+      - name: install helm-schema
+        run: go install github.com/dadav/helm-schema/cmd/helm-schema@latest
+
+      - name: test helm-schema
+        run: helm-schema --version
+
+      - name: Run Helm Schema and check the outcome
+        run: |
+          cd charts/policy-controller && helm-schema -k additionalProperties,required
+          exit_code=$(git diff --exit-code)
+          exit ${exit_code}
+
+      - name: Print a comment in case of failure
+        run: |
+          echo "The policy controller values.schema.json is not up to date or has not been produced correctly
+
+          Please, install https://github.com/dadav/helm-schema
+          And run with flag -k additionalProperties,required before pushing 
+          exit 1
+        if: |
+          failure() && github.event.pull_request.head.repo.full_name == github.repository