Add build.yml

Add a CI build step to confirm the extension can be builted
as expected.

.github/workflows/build.yml

@@ -0,0 +1,23 @@
+name: photon
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node: [ 18 ]
+    name: build
+    steps:
+      - uses: actions/checkout@v3
+      - name: Setup node
+        uses: actions/setup-node@v3
+        with:
+          node-version: ${{ matrix.node }}
+      - run: npm i
+      - run: npm run build