Update to RxSwift 6

• 更新文档以适配 RxSwift 6
• 加入 ReplayRelay
• 移除已过时的代码, 感谢 @sheruce, @professordeng, @JPlay
• 纠正错别字，修改语病, 感谢 @sheruce, @professordeng

Update to RxSwift 5

Merge pull request #33 from beeth0ven/release/2.0.0

Release/2.0.0

Add demo code to some operators

1.2.0

Merge branch 'master' of https://github.com/beeth0ven/RxSwift-Chinese…

Release 1.1.0

fix typos

1.0.0

Release 1.0.0

0.2.0

Release 0.2.0

0.1.1

Publish 0.1.1

0.1.0

Add Hot and Cold Observables Link