introduce eslint

.github/workflows/lint.yml

@@ -0,0 +1,20 @@
+name: Lint
+
+on: [push, pull_request]
+
+jobs:
+  lint:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: Setup Node.js
+      uses: actions/setup-node@v1
+      with:
+        node-version: 16.x
+    - name: Install
+      run: npm i
+    - name: Lint
+      run: npm run lint