Add GitHub workflow for integration tests

.fernignore

@@ -2,6 +2,7 @@
 
 README.md
 
+.github/workflows/integration.yml
 src/wrapper
 src/index.ts
 src/errors/SquareError.ts

.github/workflows/integration.yml

@@ -0,0 +1,20 @@
+name: ci
+
+on: [push]
+
+jobs:
+  integration:
+    env:
+      TEST_SQUARE_TOKEN: ${{ secrets.TEST_SQUARE_TOKEN }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v3
+
+      - name: Set up node
+        uses: actions/setup-node@v3
+
+      - name: Run integration tests
+        # TODO: Replace the following 'run' statement with the following when TEST_SQUARE_TOKEN secret exists.
+        # run: yarn && yarn test:integration
+        run: yarn