Add CI

.github/workflows/tests.yml

@@ -0,0 +1,25 @@
+name: tests
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v1
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: ESLint
+        run: npm run lint
+
+      - name: Execute tests
+        run: npm test
+
+      - name: Run build
+        run: npm run build