Add github action

.github/workflows/gh-pages.yml

@@ -0,0 +1,37 @@
+name: GitHub Pages
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+  deploy:
+    runs-on: ubuntu-20.04
+    concurrency:
+      group: ${{ github.workflow }}-${{ github.ref }}
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Setup Node
+        uses: actions/setup-node@v2
+        with:
+          node-version: "16"
+          cache: "npm"
+
+      - run: npm ci
+      - run: |
+          echo 'module.exports.basePath = "/nextjs-template"' >> next.config.js
+      - run: npm run testnet:build
+        env:
+          UPLOAD_SENTRY_SOURCEMAPS: false
+
+      - run: npm run export
+
+      - name: Deploy
+        uses: peaceiris/actions-gh-pages@v3
+        if: ${{ github.ref == 'refs/heads/main' }}
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: out