Add a CI stub to enable CI workflows on branches

.github/workflows/ci.yml

@@ -0,0 +1,15 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - 'staging'
+      - 'master'
+
+jobs:
+  hello_world:
+    runs-on: ubuntu-latest
+    steps:
+      - name: print hello world
+        run: echo "hello world"