Add GitHub Actions config and remove Travis-CI

Author: pacso

.github/workflows/lint_and_test.yaml

@@ -0,0 +1,21 @@
+on: [push, pull_request]
+name: Lint & Test
+jobs:
+  rspec:
+    strategy:
+      matrix:
+        rails: ['5.2', '6.0.4', '6.1']
+        ruby: ['2.6', '2.7', '3.0']
+        exclude:
+          - rails: '5.2'
+            ruby: '3.0'
+    runs-on: ubuntu-latest
+    env:
+      RAILS_VERSION: ${{ matrix.rails }}
+    steps:
+    - uses: actions/checkout@v2
+    - uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby }}
+        bundler-cache: true
+    - run: bundle exec rake