Add workflow for Ubuntu

.github/workflows/swift.yml

@@ -7,7 +7,8 @@ on:
 permissions:
   contents: read
 jobs:
-  build:
+  build-macos:
+    name: Build and test on macOS
     runs-on: macos-latest
     steps:
       - name: Set Xcode version
@@ -20,3 +21,13 @@ jobs:
         run: swift build -v
       - name: Run tests
         run: swift test -v
+  build-ubuntu:
+    name: Build and test on Ubuntu
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+      - name: Build
+        run: swift build -v
+      - name: Run tests
+        run: swift test -v