Add CI job that verifies tests pass when using pnpm (vs. npm).

.github/workflows/ci.yml

@@ -30,6 +30,23 @@ jobs:
     - name: Run All Validations
       run: npm run ci
 
+  run-tests-pnpm:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Use pnpm latest
+      uses: pnpm/action-setup@v4
+      with:
+        version: latest
+    - name: Use Node.js latest
+      uses: actions/setup-node@v4
+      with:
+        node-version: latest
+    - name: Install dependencies
+      run: pnpm install
+    - name: Run CI Tests
+      run: npm test
+
   run-tests-webworker:
     runs-on: ubuntu-latest
     steps: