Added typescript def. file.

[soerenbf]

Using the library in a typescript react project, and would love simple typings to expose the intended use of the components.

[trevorr]

Thanks for suggesting this. I needed to make some style changes from your PR, but I've included TS definitions in the latest release, 1.0.2.

[DonGissel]

Since PR #2 and #3 have been closed and not merged, you should probably acknowledge the contributions of the authors elsewhere..? 🤔

[trevorr]

This PR is acknowledged in the commit: de313da

[trevorr]

Also in the README.md:

Thanks to Anders Gissel for suggesting a fix for IE 11 window scrolling and Søren Bruus Frank for submitting TypeScript definitions.