Migrate to GitHub actions (#319)

Author: rslawik

.github/workflows/tests.yml

@@ -0,0 +1,12 @@
+name: Tests
+on: [push, pull_request]
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+        with:
+          cache: 'npm'
+      - run: npm ci
+      - run: npm test