Github actions (#90)

.github/workflows/active_model_otp.yml

@@ -0,0 +1,43 @@
+name: Active Model OTP
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    types: [opened, synchronize, reopened, edited]
+
+jobs:
+  ci:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        gemfile: [rails_4.2, rails_5.0, rails_5.1, rails_5.2, rails_6.0, rails_6.1]
+        ruby-version: [2.3, 2.4, 2.5, 2.6, 2.7, 3.0]
+        exclude:
+          - { gemfile: rails_6.0, ruby-version: 2.3 }
+          - { gemfile: rails_6.1, ruby-version: 2.3 }
+          - { gemfile: rails_6.0, ruby-version: 2.4 }
+          - { gemfile: rails_6.1, ruby-version: 2.4 }
+          - { gemfile: rails_4.2, ruby-version: 2.7 }
+          - { gemfile: rails_4.2, ruby-version: 3.0 }
+          - { gemfile: rails_5.0, ruby-version: 3.0 }
+          - { gemfile: rails_5.1, ruby-version: 3.0 }
+          - { gemfile: rails_5.2, ruby-version: 3.0 }
+
+    env:
+      BUNDLE_GEMFILE: gemfiles/${{ matrix.gemfile }}.gemfile
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Install Ruby ${{ matrix.ruby-version }}
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby-version }}
+
+      - name: Install dependencies
+        run: bundle install
+
+      - name: Run tests with Ruby ${{ matrix.ruby-version }} and Gemfile ${{ matrix.gemfile }}
+        run: bundle exec rake