Restore inspector tests

We accidentally lost these in #1401

.github/workflows/inspector.yml

@@ -0,0 +1,18 @@
+---
+name: inspector
+
+on:
+  push:
+
+jobs:
+  test:
+    name: test
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: inspector
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+      - run: npm install
+      - run: npm test