Adds CI using GitHub Actions

Author: petergoldstein

.github/workflows/ci.yml

@@ -0,0 +1,21 @@
+name: CI 
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby-version: ['2.6', '2.7', '3.0', '3.1']
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Ruby ${{ matrix.ruby-version }}
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby-version }}
+        bundler-cache: true # 'bundle install' and cache
+    - name: Run specs 
+      run: |
+        bundle exec rake