build(typescript): add missing "types" property to package.json

[sheerlox]

Description

See related issue.

Related Issue

https://github.com/kelektiv/node-cron/issues/906

Motivation and Context

How Has This Been Tested?

Untested, just followed the TypeScript doc: https://www.typescriptlang.org/docs/handbook/declaration-files/publishing.html#including-declarations-in-your-npm-package

Screenshots (if appropriate):

Types of changes

• [X] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [X] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.
• [X] All new and existing tests passed.
• [ ] If my change introduces a breaking change, I have added a ! after the type/scope in the title (see the Conventional Commits standard).

[ncb000gt]

:tada: This PR is included in version 3.1.9 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: