use {{ cookiecutter.project_slug }} for vue container

[doomconspiracy]

https://github.com/ilikerobots/cookiecutter-vue-django/blob/a2b848a4c4de82a171b60b62aa3c19cf1e1b4a19/%7B%7Bcookiecutter.project_slug%7D%7D/local.yml#L138C15-L138C15