Update README.md

Author: priyadarshininadar

README.md

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+> We’ve introduced a major update to CometChat UI kits. Version 4 features a modular architecture that give you enhanced flexibility to build and customize your web and mobile apps. Please switch to the branch [v4](https://github.com/cometchat-pro/cometchat-chat-sample-app-android-java/tree/v4) to check out the sample app based on this version. Read about this new and upgraded version [on our docs](https://www.cometchat.com/docs/java-uikit-beta/overview).
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 # Android Java Chat App