ci: add GitHub Actions

- replace Travis

.github/workflows/tester.yml

@@ -0,0 +1,30 @@
+name: Tester
+
+on: [push, pull_request]
+
+jobs:
+  tester:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        node-version: ['10.x', '12.x', '14.x']
+      fail-fast: false
+    steps:
+      - uses: actions/checkout@v2
+      - name: Use Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v1
+        with:
+          node-version: ${{ matrix.node-version }}
+      - name: Cache NPM dependencies
+        uses: actions/cache@v1
+        with:
+          path: node_modules
+          key: ${{ runner.os }}-npm-cache
+          restore-keys: ${{ runner.os }}-npm-cache
+      - name: Install Dependencies
+        run: npm install
+      - name: Test
+        run: npm run test
+        env:
+          CI: true