create workflow (#16)

* create workflow

.github/workflows/build_package.yml

@@ -0,0 +1,20 @@
+name: build_package
+
+run-name: build
+
+on: [push]
+
+jobs:
+  build:
+    name: Swift ${{ matrix.swift }} on ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [macos-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: swift-actions/setup-swift@65540b95f51493d65f5e59e97dcef9629ddf11bf
+      - uses: actions/checkout@v4
+      - name: Build
+        run: swift build
+      - name: Run tests
+        run: swift test