feat: add typescript support

[infeng]

I think Typescript fit this library:

1. Typescript has strong type that reduce minor error in development stage.
2. Typescript can provide a better intelliSense.

Hope you rewrite in typescript or provide d.ts files.

[haxpor]

Personally I'm against typescript as just javascript is more flexible, and not to introduce more build process into the workflow. I've seen each component in react-weui is not that large, and is in a good size to not introduce more strict rule in programming flow.

That is my opinion, but decision is up to owner.

[lzp401]

Looking forward to have officially support for typescript by providing .d.ts file:)

[peterz3g]

支持官方版d.ts