Add CI workflow (#1)

Author: mattt

.github/workflows/ci.yml

@@ -0,0 +1,37 @@
+name: CI
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["main"]
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  test:
+    timeout-minutes: 5
+    strategy:
+      matrix:
+        swift-version:
+          - 6.0.3
+          - 6.1.0
+
+    runs-on: macos-latest
+    name: Test (Swift ${{ matrix.swift-version }})
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Swift on macOS
+        uses: swift-actions/setup-swift@v2
+        with:
+          swift-version: ${{ matrix.swift-version }}
+
+      - name: Build
+        run: swift build -v
+
+      - name: Run tests
+        run: swift test -v