Added types to frontend (From backend so it's easier to use)

[MrBisquit]

Added types to frontend

• Basically copied from backend
• Really simple to use
• They're all types (Except the enums)

This is just basic data structure and can help with getting things started.

[MrBisquit]

Any particular reason why the object type properties are in snake_case? I'd think camelCase should be used. Similar with type names (e.g. Notification_Type should be NotificationType - no need for the underscore). Please refer to the style guide if you're having issues with naming convention here: https://github.com/airbnb/javascript/tree/master/react

It's fine it's just I normally name stuff that way, I'll change it later.

[MrBisquit]

I literally copied the names from backend btw