Add GH action to push hydrogen theme to external repo

.github/workflows/push-to-external-repo.yml

@@ -0,0 +1,39 @@
+name: (main) push to external repo
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - "templates/hydrogen-theme/**"
+  pull_request:
+    branches:
+      - main
+    paths:
+      - "templates/hydrogen-theme/**"
+
+jobs:
+  push-to-external-repo:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Determine branch
+        id: branch
+        run: |
+          if [ "${{ github.event_name }}" == "pull_request" ]; then
+            pr_number="${{ github.event.number }}"
+            echo "branch=pull-request-${pr_number}" >> $GITHUB_OUTPUT
+          else
+            echo "branch=main" >> $GITHUB_OUTPUT
+          fi
+
+      - name: Publish to external repository
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          deploy_key: ${{ secrets.SSH_DEPLOY_KEY }}
+          publish_dir: ./templates/hydrogen-theme
+          external_repository: ${{ vars.EXTERNAL_REPO }}
+          publish_branch: ${{ steps.branch.outputs.branch }}
+          allow_empty_commit: true

templates/hydrogen-theme/README.md

@@ -14,7 +14,7 @@ Hydrogen is Shopify’s stack for headless commerce. Hydrogen is designed to dov
 - ESLint
 - Prettier
 - GraphQL generator
-- TypeScript and JavaScript flavors
+- TypeScript flavors
 - Minimal setup of components and routes
 
 ## Getting started