Export typescript definitions

[markovd18]

The library is not usable with Typescript at the moment.

Include

"exports": {
    // ...
    "types": "./types"
}

in the package.json, since right now the types are not exported and not usable. All the types in thy types directory are duplicated in the dates-holidays library for some reason and exported there. However, if one wants to use just the parser itself, types are not exported at all.