ci: add workflow for documentation update

.github/workflows/helmdocs.yaml

@@ -0,0 +1,34 @@
+---
+name: helmdocs
+
+"on":
+  push:
+    branches:
+      - master
+
+jobs:
+  helmdocs:
+    runs-on: ubuntu-20.04
+
+    steps:
+      - name: Checkout source
+        id: source
+        uses: actions/checkout@v3
+
+      - name: Update readme
+        uses: docker://jnorwood/helm-docs:v1.6.0
+        with:
+          entrypoint: helm-docs
+
+      - name: Commit changes
+        id: commit
+        uses: EndBug/add-and-commit@v9
+        with:
+          author_name: GitHub Actions
+          author_email: [email protected]
+          add: charts/
+          message: automated readme update [skip ci]
+          push: true
+          commit: --signoff
+
+...