Invert ignoredlist

[JoaoVictor834]

Is your feature request related to a problem? Please describe.
When two clans are in war, they can break or place every block exept the blocks in ignored list, then if you wants to allow only a few blocks you have to put all minecraft blocks in the ignored list exept the blocks that you want, is very annoying.

Describe the solution you'd like
Add a config option to invert the ignoredlist. To make the blocks in the list placeable and breakable.

Describe alternatives you've considered
Make the ignoredlist like the griefpreventions siege list (only the blocks in the list are allow to place/break) or add a config to invert the list.

Additional context
Sorry for my bad english,
I think this is easy to make, but i can make a pull request with this feature if you don't have time or something.

[Nishikiyama]

We have time, but if you know how to make it, why not make it and contribute :) <3