Add GitHub Actions workflow for build checks on pull requests

- Configure `.gitea/workflows/build.yaml` to run builds on `main` branch pull requests.
- Include steps for dependency installation, Node.js setup, and build execution using pnpm.

.gitea/workflows/build.yaml

@@ -0,0 +1,29 @@
+name: Build Check
+on:
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 10
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: 'pnpm'
+
+      - name: Install dependencies
+        run: pnpm install
+
+      - name: Run Build
+        run: pnpm run build