Add tests

.github/workflows/main.yml

@@ -0,0 +1,28 @@
+name: CI
+
+on:
+  - push
+  - pull_request
+
+jobs:
+  test:
+    name: Node.js ${{ matrix.node-version }} on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      fail-fast: false
+      matrix:
+        node-version: [ 18, 20, 21 ]
+        os: [ ubuntu-latest, macos-latest, windows-latest ]
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: ${{ matrix.node-version }}
+      - name: Install dependencies
+        run: yarn install --ignore-engines
+      - name: AVA
+        run: yarn ava
+      - name: XO
+        run: yarn xo