github: Add workflow to trigger website build on docs/ update

Signed-off-by: Joaquim Rocha <joaquim.rocha@microsoft.com>

.github/workflows/trigger-website-build.yml

@@ -0,0 +1,22 @@
+name: Trigger Headlamp website update
+
+# See https://github.com/headlamp-k8s/headlamp-website
+on:
+  push:
+    paths:
+      - 'docs/**'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  trigger_flatpak_update:
+    name: Trigger Headlamp website update
+    runs-on: ubuntu-latest
+    steps:
+      - name: Trigger via gh
+        env:
+          GITHUB_TOKEN: ${{ secrets.KINVOLK_REPOS_TOKEN }}
+        run: |
+          gh api repos/flathub/io.kinvolk.Headlamp/dispatches --raw-field event_type=headlamp-docs-update