[IMPROVE] Project-restructure

[abhinavkrin]

Brief Title

This PR introduces mono repo to our EmbeddedChat project.

Acceptance Criteria fulfillment

• Converted the project into mono repo
• Created auth package for embeddedchat. It now supports password flow and oauth token flow.
• Restructed API into @embeddedchat/api package and used @embedded/auth for all authentication purpose.
• Created playground for both auth and API package.

Fixes #216 #215 #214

Video/Screenshots

[sidmohanty11]

Thanks @abhinavkrin LGTM