Check nightly action on CI

Author: kateinoigakukun

.github/workflows/test.yml

@@ -32,3 +32,9 @@ jobs:
       with:
         swift-version: ${{ matrix.swift-version }}
     - run: swift --version
+  test-nightly:
+    runs-on: ubuntu-20.04
+    steps:
+    - uses: actions/checkout@v3
+    - uses: ./nightly
+    - run: swift --version