MNT Add workflow files

.github/workflows/ci.yml

@@ -0,0 +1,11 @@
+name: CI
+
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  ci:
+    name: CI
+    uses: silverstripe/gha-ci/.github/workflows/ci.yml@v1

.github/workflows/keepalive.yml

@@ -0,0 +1,17 @@
+name: Keepalive
+
+on:
+  # At 6:30 AM UTC, on day 11 of the month
+  schedule:
+    - cron: '30 6 11 * *'
+  workflow_dispatch:
+
+jobs:
+  keepalive:
+    name: Keepalive
+    # Only run cron on the silverstripe account
+    if: (github.event_name == 'schedule' && github.repository_owner == 'silverstripe') || (github.event_name != 'schedule')
+    runs-on: ubuntu-latest
+    steps:
+      - name: Keepalive
+        uses: silverstripe/gha-keepalive@v1