Add GitHub workflow

Author: Pattio

.github/workflows/ci.yml

@@ -0,0 +1,18 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  macos-test:
+    runs-on: macos-latest
+
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v4
+
+      - name: Run tests
+        run: swift test --parallel