👷(helm) add CI for publishing Helm charts

We need to publish a Helm chart to facilitate separating the code from
the deployment configuration.

.github/workflows/release-helmchart.yml

@@ -0,0 +1,35 @@
+name: Release Chart
+run-name: Release Chart
+
+on:
+  push:
+    branches:
+      - 'main'
+    paths:
+      - ./src/helm/desk/**
+
+jobs:
+  release:
+    permissions:
+      contents: write
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Cleanup
+        run: rm -rf ./src/helm/extra
+
+      - name: Install Helm
+        uses: azure/setup-helm@v4
+        env:
+          GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
+
+      - name: Publish Helm charts
+        uses: numerique-gouv/helm-gh-pages@add-overwrite-option
+        with:
+          charts_dir: ./src/helm
+          linting: on
+          token: ${{ secrets.GITHUB_TOKEN }}