Add support for Windows

まだ誰も着手していません。

With React Native for Windows becoming a viable target, enabling this package for Windows would be a great benefit to the community! (Especially if this package backs `uuid`, since a library I plan on using in RN uses it.)

I'm willing to take a stab at an initial implementation, and wanted to post this issue as a place to track progress.

Todo:
- [x] ~~Ensure RN for Windows supports synchronous methods~~ It does!
- [x] ~~Decide if C++ or C# would be the most appropriate~~ C# would be the most approachable, and would be just as performant as the C++ version since they're both just calling UWP APIs
- [x] ~~Determine if RN prefers Win32, UWP, or both for third party modules~~ RN for Windows only works on Windows 10, so there's no sense in using the Win32 APIs.
- [x] Setup project (blocked by https://github.com/microsoft/react-native-windows/issues/4211)
- [ ] Rewrite module in C++ (blocked by https://github.com/microsoft/react-native-windows/issues/4215)

ファイル、テスト、エントリポイントは指定されていません。まず、完了したセットアップの決定事項とリンクされた react-native-windows のブロッカーを確認してください。モジュールが Windows をサポートする動作する C++ 実装を備えた時点で、この issue は完了です。

索引モデルが issue の本文から書いたものです。