Add workflow to check schema.json is up-to-date

Author: justinfagnani

.github/workflows/tests.yaml

@@ -0,0 +1,19 @@
+name: Test
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+        with:
+          node-version: 16
+      - run: npm ci
+      - run: npm run build
+      - name: Check schema.json is up-to-date
+        run: git diff --exit-code