ci: Set up CI testing

.github/workflows/ci.yml

@@ -0,0 +1,34 @@
+name: CI
+
+on: [push, pull_request]
+
+jobs:
+  build:
+
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      matrix:
+        os: [windows-latest, macOS-latest, ubuntu-latest]
+        node-version: [20.x]
+        deno-version: [1.x]
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v4
+      with:
+        node-version: ${{ matrix.node-version }}
+
+    - name: Set up Deno ${{ matrix.deno-version }}
+      uses: denolib/setup-deno@v2
+      with:
+        deno-version: ${{ matrix.deno-version }}
+
+    - name: npm install, build, and test
+      run: |
+        npm install
+        npm test
+      env:
+        CI: true