Is your feature request related to a problem? Please describe.
Currently, the only barrier for every dimension is obsidian. I'd love for this to be configurable for progression-based modpacks with multiple dimensions.

Describe the solution you'd like
Add a config option (see my previous issue about dim stack config) for each dimension that determines what block should be at the bottom of that dimension.

Describe alternatives you've considered
n/a

Additional context
n/a

Already implemented.