Add GitHub Actions CI configuration

Set up CI workflow for testing and linting

.github/workflows/main.yml

@@ -1,3 +1,26 @@
-npm ci
-npm test
-npm run lint
+name: CI
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Run tests
+        run: npm test