fix: Add 'main' and 'types' entries to package.json

[nzakas]

Prerequisites checklist

• [x] I have read the contributing guidelines.

What is the purpose of this pull request?

Add main and types entries to package.json files. Even though we have exports specified, some tools still rely on these old, top-level entries.

What changes did you make? (Give an overview)

• Added main and types entries to package.json files in compat, config-array, and object-schema.

Related Issues

fixes #46

Is there anything you'd like reviewers to focus on?