Add CI workflow

.github/workflows/nextjs.yml

@@ -0,0 +1,40 @@
+name: Build frontend
+
+on:
+  push:
+    branches: ['main']
+  pull_request:
+    branches: ['main']
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+      - name: Restore cache
+        uses: actions/cache@v4
+        with:
+          path: |
+            .next/cache
+          # Generate a new cache whenever packages or source files change.
+          key: ${{ runner.os }}-nextjs-${{ hashFiles('**/package-lock.json', '**/yarn.lock') }}-${{ hashFiles('**.[jt]s', '**.[jt]sx') }}
+          # If source files changed but packages didn't, rebuild from a prior cache.
+          restore-keys: |
+            ${{ runner.os }}-nextjs-${{ hashFiles('**/package-lock.json', '**/yarn.lock') }}-
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Lint
+        run: npx --no-install next lint
+
+      - name: Format
+        run: npm run format
+
+      - name: Build with Next.js
+        run: npx --no-install next build