chore(gha): impl lint workflow

Implements "lint" workflow to run "npm run lint" on every PR against
`master` branch

.github/workflows/lint.yml

@@ -0,0 +1,23 @@
+name: lint
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+
+jobs:
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v1
+        with:
+          node-version: '14.x'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Run "npm run lint"
+        run: npm run lint