Add GitHub Actions workflow for testing

.github/workflows/test.yml

@@ -0,0 +1,35 @@
+name: Tests
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+      
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+      
+      - name: Install dependencies
+        run: npm ci
+      
+      - name: Run tests
+        run: npm test
+      
+      - name: Upload coverage reports (optional)
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-report
+          path: coverage/
+          retention-days: 30