git:add build workflow

.github/workflows/frontend_build.yml

@@ -0,0 +1,39 @@
+name: Build React App
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Set up Node.js
+      uses: actions/setup-node@v1
+      with:
+        node-version: '20'
+
+    - name: Install pnpm
+      run: npm install -g pnpm
+
+    - name: Install frontend dependencies with pnpm
+      run: |
+        cd frontend
+        pnpm install
+
+    - name: Build frontend with pnpm
+      run: |
+        cd frontend
+        pnpm run build
+
+    - name: Deploy to GitHub Pages
+      uses: JamesIves/[email protected]
+      with:
+        branch: gh-pages  
+        folder: frontend/build 
+        token: ${{ secrets.GITHUB_TOKEN }}