feat: create a new docs website (#2525)

## Summary:

I had previously created a documentation website in a new repo at
r[eact-native-macos-docs](https://github.com/microsoft/react-native-macos-docs),
however due to how Github Pages works, I can't easily publish that to
microsoft.github.io/react-native-macos. So... let's move it here.

## Test Plan:

`yarn start` deploys the website locally, successfully.

Author: Saadnajmi

.github/dependabot.yml

@@ -0,0 +1,18 @@
+# Basic `dependabot.yml` file with
+# minimum configuration for three package managers
+
+version: 2
+updates:
+  - package-ecosystem: "npm"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    groups:
+      docusaurus:
+        patterns:
+          - "@docusaurus/*"
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

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

@@ -0,0 +1,34 @@
+name: Build Website
+
+on:
+  workflow_call:
+    outputs:
+      build-path:
+        description: "Path to the build directory"
+        value: ${{ jobs.build.outputs.build-path }}
+
+jobs:
+  build:
+    name: "Build the website"
+    runs-on: ubuntu-24.04
+    outputs:
+      build-path: ./build
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+      - name: Install dependencies
+        run: yarn
+        working-directory: ./docsite
+      - name: Build website
+        run: yarn build
+        working-directory: ./docsite
+      - name: Upload build artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: website-build
+          path: ./docsite/build
+          retention-days: 1

.github/workflows/microsoft-pr.yml

@@ -0,0 +1,38 @@
+name: PR
+
+on:
+  pull_request:
+    types: [opened, synchronize, edited]
+    branches: [ "main" ]
+
+concurrency:
+  # Ensure single build of a pull request. `main` should not be affected.
+  group: ${{ github.workflow }}-${{ github.ref }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  lint-commit:
+    name: "Lint PR title"
+    permissions: {}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          filter: blob:none
+          fetch-depth: 0
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+      # We lint the PR title instead of the commit message to avoid script injection attacks.
+      # Using environment variables prevents potential security vulnerabilities as described in:
+      # https://docs.github.com/en/actions/security-for-github-actions/security-guides/security-hardening-for-github-actions#example-of-a-script-injection-attack
+      - name: Lint PR title
+        env:
+          PR_TITLE: ${{ github.event.pull_request.title }}
+        run: |
+          echo "$PR_TITLE" | npx @rnx-kit/[email protected]
+  build-website:
+    name: "Build the website"
+    permissions: {}
+    uses: ./.github/workflows/microsoft-build-website.yml
+

.github/workflows/microsoft-publish.yml

@@ -0,0 +1,54 @@
+name: Deploy to GitHub Pages
+
+on:
+  # Runs on pushes targeting the default branch
+  push:
+    branches: ["main"]
+
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+# Allow only one concurrent deployment, skipping runs queued between the run
+# in-progress and latest queued. However, do NOT cancel in-progress runs as we
+# want to allow these production deployments to complete.
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  # Build job
+  build:
+    uses: ./.github/workflows/microsoft-build-website.yml
+
+  # Prepare for Pages deployment
+  prepare-pages:
+    runs-on: ubuntu-24.04
+    needs: build
+    steps:
+      - name: Download build artifacts
+        uses: actions/download-artifact@v4
+        with:
+          name: website-build
+          path: ./docsite/build
+      - name: Upload Pages artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: ./docsite/build
+
+  # Deployment job
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-24.04
+    needs: prepare-pages
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4