Add submodule to git workflow checkout

Author: bettse

.github/workflows/main.yml

@@ -7,6 +7,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v3
+        with:
+          submodules: 'true'
       - name: Build with ufbt
         uses: flipperdevices/[email protected]
         id: build-app