add PR workflow

.github/workflows/pr.yml

@@ -0,0 +1,17 @@
+name: Pull request tests
+
+on: [pull_request]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: actions/setup-node@v2
+        with:
+          node-version: 14
+
+      - run: yarn
+      - run: npm run lint