add: terraform doc github action

.github/workflows/documentation.yml

@@ -0,0 +1,19 @@
+name: Generate terraform docs
+on:
+  - pull_request
+
+jobs:
+  docs:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          ref: ${{ github.event.pull_request.head.ref }}
+
+      - name: Render terraform docs and push changes back to PR
+        uses: terraform-docs/gh-actions@main
+        with:
+          working-dir: .
+          output-file: README.md
+          output-method: inject
+          git-push: "true"