Add GitHub Actions CI workflow

- Runs on push to main and all pull requests
- Includes lint, typecheck, and test steps
- Uses Node.js 20 with npm caching for faster builds

Author: ZainRizvi

.github/workflows/ci.yml

@@ -0,0 +1,31 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: ['*']
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - 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: Lint
+        run: npm run lint
+
+      - name: Type check
+        run: npm run typecheck
+
+      - name: Test
+        run: npm test