Replace Travis CI with GitHub Actions build/lint/test workflows (#39)

.github/workflows/test.yml

@@ -0,0 +1,17 @@
+name: Run tests
+
+on: [push]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install dependencies
+        uses: borales/actions-yarn@v2.0.0
+        with:
+          cmd: install
+      - name: Run unit tests
+        uses: borales/actions-yarn@v2.0.0
+        with:
+          cmd: test