treefmt.toml schema

[tomodachi94]

Since SchemaStore/schemastore#4988, there is now a JSON schema for treefmt.toml.

This allows LSPs like Taplo and Tombi to validate treefmt.tomls statically, as well as to autocomplete configuration options inside of editors. This makes the user experience much better.

The schema: https://schemastore.org/treefmt.json