Add TypeScript declarations

[jtiala]

Thanks for the great library! TypeScript declarations would be sweet.

[dmerrill6]

Thanks for the kind words!

Would love to convert the lib to typescript eventually, but for the short term adding type declarations is a nice idea. I am a bit busy these days but as soon as I add them I'll let you know.

[jtiala]

Any news on this project? I can try to help you with the three issues I created if you are willing to accept pull requests.

[dmerrill6]

Hey @jtiala!

I'm really sorry I haven't had the bandwidth to solve these issues. I'd be happy to review any pull requests and release a new version as soon as they get merged.

Thanks!