text: Title: Make challenge submission attempt rate limiting configurable
  Body: Sometimes people end up hitting this rate limit too soon so we should make it configurable in the config panel. 
  
  https://github.com/CTFd/CTFd/blob/7fc05bd4e3bf18606871a0ba6ad11f70e2be77e0/CTFd/api/v1/challenges.py#L624-L648
  
  Instead of a hard limit of 10 we should have an option to set the number and perhaps disable it.