lint: run linter using GH Actions

.github/workflows/ci.yml

@@ -0,0 +1,15 @@
+name: Linter
+
+on: [pull_request]
+
+jobs:
+  run-linter:
+    name: Run Linter
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-node@v1
+      with:
+        node-version: '12.x'
+    - run: npm install
+    - run: npm run lint