Add docs build and deploy github action

Problem: NGINX docs have migrated off netlify

Solution: This action will deploy to the new infrastructure, and
remove Netlify configuration from this project.

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

@@ -0,0 +1,40 @@
+name: Build and deploy docs
+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:
+    - "site/**"
+
+permissions:
+  contents: read
+
+jobs:
+  call-docs-build-push:
+    if: ${{ github.event.repository.fork == false }}
+    uses: nginxinc/docs-actions/.github/workflows/docs-build-push.yml@03a9a3808fcb77cd0c19d7fa5d59b25565dd1d6d # v1.0.2
+    permissions:
+      pull-requests: write # needed to write preview url comment to PR
+      contents: read
+    with:
+      production_url_path: "/nginx-gateway-fabric/"
+      preview_url_path: "/previews/nginx-gateway-fabric/"
+      docs_source_path: "public/nginx-gateway-fabric"
+      docs_build_path: "./site"
+      doc_type: "hugo"
+      environment: ${{ inputs.environment }}
+    secrets:
+      AZURE_CREDENTIALS: ${{ secrets.AZURE_CREDENTIALS_DOCS }}
+      AZURE_KEY_VAULT: ${{ secrets.AZURE_KEY_VAULT_DOCS }}

site/README.md

@@ -2,7 +2,7 @@
 
 This directory contains all of the user documentation for NGINX Gateway Fabric, as well as the requirements for building and publishing the documentation.
 
-Documentation is written in Markdown, built using [Hugo](https://gohugo.io) with [nginx-hugo-theme](https://github.com/nginxinc/nginx-hugo-theme), then deployed with [Netlify](https://www.netlify.com/).
+We write our documentation in Markdown. We build it with [Hugo](https://gohugo.io) and our custom [NGINX Hugo theme](https://github.com/nginxinc/nginx-hugo-theme). We set up previews and deployments using our [docs-actions](https://github.com/nginxinc/docs-actions?tab=readme-ov-file#docs-actions) workflow.
 
 ## Setup