Add CI build and check actions

.github/workflows/ci.yml

@@ -0,0 +1,46 @@
+name: Continuous integration
+on: [push, pull_request]
+
+jobs:
+  check:
+    name: Build and check
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Install pnpm
+        uses: pnpm/action-setup@v3
+        with:
+          version: ">=8"
+
+      - name: Get pnpm store directory
+        shell: bash
+        run: |
+          echo "STORE_PATH=$(pnpm store path --silent)" >> $GITHUB_ENV
+
+      - uses: actions/cache@v4
+        name: Setup pnpm cache
+        with:
+          path: ${{ env.STORE_PATH }}
+          key: ${{ runner.os }}-pnpm-store-${{ hashFiles('**/pnpm-lock.yaml') }}
+          restore-keys: |
+            ${{ runner.os }}-pnpm-store-
+
+      - name: Install dependencies
+        run: pnpm install
+
+      - name: Build code
+        run: pnpm build
+
+      - name: Check code
+        run: pnpm check
+
+      - name: Format code
+        run: pnpm fmt:check