[Feature request] Negative selection radius

[jonalange]

Not sure if this is already possible or not, but I couldn't find something in the wiki.

At first I thought that selection radius will make the selection smaller around my filters, but actually it does increase the selection.

It would be great to enter negative values. To add a little padding around selected chunks.
The reason why this would be useful is to not have bases in a completely unknown environment of the player, but keep some "known terrain" around bases and points of interest.