text: Title: Make CORS configurable from an environment variable
  Body: ## Tell us about the problem you're trying to solve
  
  Currently, CORS is enabled by default for the API server. Refer: https://github.com/chaos-genius/chaos_genius/blob/d0d2922ac8bddbf9cc9b20ee6f76d477725fd85c/chaos_genius/app.py#L52
  
  For security reasons, CORS should be disabled by default. Refer: https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS
  
  ## Describe the solution you'd like
  
  A variable needs to be added in settings.py (https://github.com/chaos-genius/chaos_genius/blob/d0d2922ac8bddbf9cc9b20ee6f76d477725fd85c/chaos_genius/settings.py) to enable/disable CORS. By default, CORS will be disabled.
  
  The variable will also need to be added in the .env (https://github.com/chaos-genius/chaos_genius/blob/d0d2922ac8bddbf9cc9b20ee6f76d477725fd85c/.env) and all of the docker-compose files.
  
  ## Describe alternatives you've considered
  
  N/A
  
  ## Additional context
  
  N/A
  
  Please leave a reply or reach out to us on our [community slack](https://github.com/chaos-genius/chaos_genius#octocat-community) if you need any help.
  