Add PR workflow

.github/workflows/pr.yml

@@ -0,0 +1,15 @@
+name: Test PR
+
+on: pull_request
+
+jobs:
+
+  build_and_test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v1
+        with:
+          node-version: 14.x
+      - run: yarn install
+      - run: yarn test