@metamask/build-utils: Convert @types/eslint to production dependency

[rekmarks]

Explanation

Following the recommendation of @mcmire, converts @types/eslint from a dev to production dependency of @metamask/build-utils.

The reason:

ESLint will show up in the type definition file for src/transforms/utils.ts, so anyone who uses this library in a TypeScript will need that type in order to compile their code.

References

• Add @metamask/build-utils package #3577 (comment)

Changelog

N/A (package unreleased)

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've highlighted breaking changes using the "BREAKING" category above as appropriate

[mcmire]

Looks good!