MNT Use GitHub Actions CI

.github/workflows/ci.yml

@@ -0,0 +1,16 @@
+name: CI
+
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+  # Every Saturday at 11:30am UTC
+  schedule:
+    - cron: '30 11 * * 6'
+
+jobs:
+  ci:
+    name: CI
+    # Only run cron on the silverstripe account
+    if: (github.event_name == 'schedule' && startsWith(github.repository, 'silverstripe/')) || (github.event_name != 'schedule')
+    uses: silverstripe/gha-ci/.github/workflows/ci.yml@v1

.github/workflows/keepalive.yml

@@ -0,0 +1,17 @@
+name: Keepalive
+
+on:
+  workflow_dispatch:
+  # The 4th of every month at 10:50am UTC
+  schedule:
+    - cron: '50 10 4 * *'
+
+jobs:
+  keepalive:
+    name: Keepalive
+    # Only run cron on the silverstripe account
+    if: (github.event_name == 'schedule' && startsWith(github.repository, 'silverstripe/')) || (github.event_name != 'schedule')
+    runs-on: ubuntu-latest
+    steps:
+      - name: Keepalive
+        uses: silverstripe/gha-keepalive@v1

README.md

@@ -1,6 +1,6 @@
 # Subsites Module
 
-[![Build Status](https://api.travis-ci.com/silverstripe/silverstripe-subsites.svg?branch=2)](https://travis-ci.com/silverstripe/silverstripe-subsites)
+[![CI](https://github.com/silverstripe/silverstripe-subsites/actions/workflows/ci.yml/badge.svg)](https://github.com/silverstripe/silverstripe-subsites/actions/workflows/ci.yml)
 [![Scrutinizer Code Quality](https://scrutinizer-ci.com/g/silverstripe/silverstripe-subsites/badges/quality-score.png?b=master)](https://scrutinizer-ci.com/g/silverstripe/silverstripe-subsites/?branch=master)
 [![codecov](https://codecov.io/gh/silverstripe/silverstripe-subsites/branch/master/graph/badge.svg)](https://codecov.io/gh/silverstripe/silverstripe-subsites)
 [![SilverStripe supported module](https://img.shields.io/badge/silverstripe-supported-0071C4.svg)](https://www.silverstripe.org/software/addons/silverstripe-commercially-supported-module-list/)