Add test workflow to execute on pull requests to main

.github/workflows/test.yml

@@ -0,0 +1,24 @@
+name: Ledger Accountable Test Workflow
+
+on:
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Check out code
+      uses: actions/checkout@v2
+
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: 2.7.8
+
+    - name: Install dependencies
+      run: bundle install
+
+    - name: Run tests
+      run: rake test