Added github workflow

.github/workflows/swift.yml

@@ -0,0 +1,28 @@
+name: Swift
+
+on: [push]
+
+jobs:
+  build:
+
+    runs-on: macOS-latest
+    strategy:
+          matrix:
+            destination: ['platform=iOS Simulator,OS=13.1,name=iPhone 11']
+            xcode: ['/Applications/Xcode_12.app/Contents/Developer']
+    steps:
+    - uses: actions/checkout@v1
+    # Github Actions' machines do in fact have recent versions of Xcode,
+    # but you may have to explicitly switch to them.  We explicitly want
+    # to use Xcode 12, so we use xcode-select to switch to it.
+    - name: Switch to Xcode 12
+      run: sudo xcode-select --switch /Applications/Xcode_12.app
+    # Since we want to be running our tests from Xcode, we need to
+    # generate an .xcodeproj file.  Luckly, Swift Package Manager has
+    # build in functionality to do so.
+    - name: Generate xcodeproj
+      run: swift package generate-xcodeproj
+    # Finally, we invoke xcodebuild to run the tests on an iPhone 11
+    # simulator.
+    - name: Run tests
+      run: xcodebuild test -destination 'name=iPhone 11' -scheme 'ObjectUI-Package'