Add GitHub Action for site and preview deployments

Author: danielledeleo

.github/workflows/docs-build-push.yml

@@ -0,0 +1,36 @@
+name: Build and deploy docs (unit.nginx.org)
+on:
+  workflow_dispatch:
+    inputs:
+      environment:
+        description: 'Environment to deploy to'
+        required: true
+        default: 'preview'
+        type: choice
+        options:
+        - preview
+        - dev
+        - staging
+        - prod
+  pull_request:
+    branches:
+      - "*"
+    paths:
+      - "docs/**"
+
+jobs:
+  call-docs-build-push:
+    uses: nginxinc/docs-actions/.github/workflows/docs-build-push.yml@main
+    permissions:
+      pull-requests: write # needed to write preview url comment to PR
+      contents: read
+    with:
+      production_url_path: ""
+      preview_url_path: "/previews/unit"
+      docs_source_path: "deploy"
+      docs_build_path: "."
+      doc_type: "sphinx"
+      environment: ${{inputs.environment}}
+    secrets:
+      AZURE_CREDENTIALS: ${{secrets.AZURE_CREDENTIALS}}
+      AZURE_KEY_VAULT: ${{secrets.AZURE_KEY_VAULT}}

README.md

@@ -17,6 +17,12 @@ pip install -r requirements.txt
 make serve
 ```
 
+Commits in any branch associated with a Pull Request, if made by a maintainer, will automatically deploy a preview site. A comment with a link to the preview will show up in the PR.
+
+## Deployment
+
+See the [`docs-actions` README](https://github.com/nginxinc/docs-actions/tree/main?tab=readme-ov-file#docs-actions).
+
 ## Contributing
 
 Pull requests are welcome. For major changes, please open an issue