add preview

.github/workflows/preview.yml

@@ -0,0 +1,33 @@
+name: Deploy PR previews
+concurrency: preview-${{ github.ref }}
+on:
+  pull_request:
+    types:
+      - opened
+      - reopened
+      - synchronize
+      - closed
+jobs:
+  deploy-preview:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: 2.7
+          bundler-cache: true
+      - name: Setup Node
+        uses: actions/setup-node@v2
+        with:
+          node-version: '14'
+      - run: npm install
+      - name: Build site
+        uses: limjh16/jekyll-action-ts@v2
+        with:
+          enable_cache: true
+      - uses: rossjrw/pr-preview-action@v1
+        with:
+          source-dir: .
+          preview-branch: gh-pages
+          umbrella-dir: _site/pr-preview
+          action: auto