fix: add types to exports

[SimenB]

See https://www.typescriptlang.org/docs/handbook/esm-node.html#packagejson-exports-imports-and-self-referencing

[rcari]

@dcodeIO this is needed to avoid breaking Typescript when using moduleResolution: "node16".

[rcari]

Thanks for merging this @dcodeIO
Any chance you could cut a new version of the package?

[dcodeIO]

If the setup still works, this should happen automatically around 0 UTC.