Use our own mod metadata

[CursedFlames]

Currently we don't modify fabric-api's metadata; before release we'll want to replace this with our own metadata (possibly either keep modid the same for compatiblity, or use provides).

Ideally we'll also want some way to avoid Gambeson loading on fabric, to avoid confusion - possibly Steelwool's internal mod should have (fabric-side) modid steelwool-loader or similar and provide fabric-loader instead; we can then specify a dependency on steelwool-loader.