Checkout submodules recursively for dotnet-format step

Fixes #10

Author: kzu

.github/workflows/build.yml

@@ -21,6 +21,10 @@ jobs:
     steps:
       - name: 🤘 checkout
         uses: actions/checkout@v2
+        with: 
+          submodules: recursive
+          fetch-depth: 0
+
       - name: ✓ ensure format
         run: |
           dotnet tool update -g dotnet-format --version 5.0.*