Offer a way to configure perks when a user has donated x amount

[lewk-io]

As a server owner I would like to be able to give my players a perk when they have donated x amount of money.

For example:

A user has donated £110.
Because they have donated over £100 I would like to give them the role "Very kind donator".

Another user has donated £275.
Because they have donated over £250 I would like give them the role "Super very kind donator".
I may also want to configure that a user can only have one of these roles.