ci: add cross-platform testing to prevent platform-specific regressions

This adds GitHub Actions workflow to test on Ubuntu, Windows, and macOS.
This is optional and can be removed if the maintainers prefer.

Related to #16179

.github/workflows/tests.yml

@@ -0,0 +1,30 @@
+name: Tests
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        node-version: [18, 20]
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Setup Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v3
+        with:
+          node-version: ${{ matrix.node-version }}
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build
+        run: npm run build
+
+      - name: Run tests
+        run: npm test