Add "minSize" config option

[arschfidel0815]

Is it possible to add a minSize config option similar to the maxSize option that already exists?

So for example by setting minSize to 6, portals smaller than the vanilla Minecraft minimum portal size wouldn't work.
I'd really like this for my survival server, so that one would still need at least 10 obsidian to build a portal.

There also already is the enforceMinimum option, but it has a fixed minimum of a 1x2 block sized portal, that unfortunately cannot be changed.

I would love to see this feature added and thanks for the already great mod!