set default branch as main in github workflow

Author: mustafasoylu

.github/workflows/deploy_demo.yml

@@ -17,6 +17,7 @@ jobs:
       run: |
         git config --global user.email "deploy-fair-python-cookiecutter@example.com"
         git config --global user.name "Deployment Bot"
+        git config --global init.defaultBranch main
 
     - name: Prepare SSH (needed for remote push)
       uses: webfactory/ssh-agent@v0.7.0