fix: type reference in package.json

[stefanhar]

Types seem to be broken in current release causing: Could not find a declaration file for module 'nestjs-dataloader'.

[dhritzkiv]

This PR closes #60

Any chance for this to be reviewed and published to npm?

[wereHamster]

This package is just one .ts file, it's easier to copy&paste into your project rather than waiting for upstream to fix 😉

[wjamilaion]

@krislefeber can you please review this PR and merge, and release the newer version?