Add github workflow (#1)

.github/workflows/pr.yaml

@@ -0,0 +1,15 @@
+name: run tests
+on: [pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: npm test
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20.x'
+      - run: npm ci
+      - run: npm test
+