ci: automatically run tests

.github/workflows/swift.yml

@@ -0,0 +1,15 @@
+name: Swift
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+jobs:
+  build:
+    runs-on: macos-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Build
+      run: swift build -v
+    - name: Run tests
+      run: swift test -v