GitHub actions should checkout submodules too

Author: grafolean

.github/workflows/on_release.yml

@@ -11,7 +11,9 @@ jobs:
     steps:
 
     - name: Checkout source code
-      uses: actions/checkout@v1
+      uses: actions/checkout@v2
+      with:
+        submodules: 'true'
 
 
     - name: Deploy to Docker Hub