Catch errors and display to users

[SimChadha]

There's a variety of errors that occur in the app that cause an exception instead of just notifying the user. Instead of the app crashing or generating an exception, we need to validate the data the user provides and display error text if necessary.

• [ ] Error for failed user log in
  • [ ] Generic error text if credentials don't match
• [ ] Error if not enough fields are provided when making an event
• [ ] Errors when making account if anything goes wrong

[SimChadha]

As per conversation at GM: Create an error toast component that displays an error whenever a backend error is received. From there, this toast should show up on all errors, and prevent us from having to build error logic in every place. @dylan-pham @elliot-goodman