Been doing this today and had some success.
Using these generators you can easily make the .json files needed
https://misode.github.io/dimension/
https://misode.github.io/worldgen/biome/
https://misode.github.io/dimension-type/
I have them structured like this:
resources/data/<yourmodname>/
├── dimension/<your_dimension>.json
├── dimension_type/<your_dimension_type>.json
└── worldgen/biome/<your_biome_name>.json
Again, im just starting out but this is currently working.