Adds nightly action.

.github/workflows/nightly.yml

@@ -0,0 +1,17 @@
+name: Nightly build and test
+
+on:
+  schedule:
+    - cron: '42 0 * * *'
+
+jobs:
+  build:
+
+    runs-on: macos-12
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Build
+      run: swift build -v
+    - name: Run tests
+      run: swift test -v

.github/workflows/swift.yml

@@ -1,4 +1,4 @@
-name: Swift
+name: Merge or commit
 
 on:
   push: