Run tests on CI

This is very much just GitHub's suggested node.js workflow file, with
the node versions changed. I don't know what our minimum requirements
are, but their defaults of versions 14.x, 16.x, and 18.x, all failed
from missing APIs. As of right now, 20.x and 21.x are both
current/active in the release schedule:
https://nodejs.org/en/about/previous-releases#release-schedule

.github/workflows/node.js.yml

@@ -0,0 +1,31 @@
+# This workflow will do a clean installation of node dependencies, cache/restore them, build the source code and run tests across different versions of node
+# For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-nodejs
+
+name: Node.js CI
+
+on:
+  push:
+    branches: [ "trunk" ]
+  pull_request:
+    branches: [ "trunk" ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        node-version: [20.x, 21.x]
+        # See supported Node.js release schedule at https://nodejs.org/en/about/releases/
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Use Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v3
+      with:
+        node-version: ${{ matrix.node-version }}
+        cache: 'npm'
+    - run: npm ci
+    - run: npm run build --if-present
+    - run: npm test