feat(modrinth): add the Modrinth SDK

[Mkassabov]

Caution

STOP — there is already an open distilled PR for Modrinth by someone else. Distilled's generator pipeline has changed a lot; this is a new implementation, not a rebase of theirs. Review both and do not merge this and theirs blindly.

• @JVictorV — feat(modrinth): add Modrinth SDK package #287

This is the requested Modrinth SDK. distilled#287 is an existing Modrinth SDK PR (not an issue); this PR is a new generator-pipeline implementation of the same request.

Adds @distilled.cloud/modrinth, generated from a first-party API description.

• Related PR: feat(modrinth): add Modrinth SDK package #287
• Fetch script: stacks/distilled-submodules/spec-repos/modrinth/fetch-specs.ts
• Spec source: https://docs.modrinth.com/openapi.yaml
• Convert/generate: packages/modrinth/scripts/{convert,generate}.ts
• Mirror repo distilled-mirror/spec-mirror-modrinth is created by the distilled-submodules stack on merge to main. Until then, regenerate with pnpm specs:local modrinth and DISTILLED_SPECS_LOCAL=1 pnpm generate modrinth.

pnpm specs:link modrinth recorded the .gitmodules stanza (shallow = true).