CI: add github actions for testing

Author: aramprice

.github/dependabot.yml

@@ -0,0 +1,7 @@
+---
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"

.github/workflows/ruby.yml

@@ -0,0 +1,14 @@
+name: ruby
+on:
+  push:
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true # runs 'bundle install' and caches installed gems automatically
+      - run: bundle exec rspec