Add test workflow

Author: colinmcneil

.github/workflows/test-extension.yml

@@ -0,0 +1,15 @@
+name: Test Extension
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - run: npm install
+      - run: npm run build
+      - run: npm run test