Add CI workflow

.github/workflows/ci.yml

@@ -0,0 +1,34 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    
+jobs:
+  linux:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        container:
+           - 'swift:5.5-focal'
+    container: ${{ matrix.container }}
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Run tests
+        run: swift test --sanitize=thread
+  macos:
+    runs-on: macos-11
+    strategy:
+      matrix:
+        xcode:
+          - '13.1'
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Select Xcode ${{ matrix.xcode }}
+        run: sudo xcode-select -s /Applications/Xcode_${{ matrix.xcode }}.app
+      - name: Run tests
+        run: swift test --sanitize=thread