React Core and Components

The React SDK by LiveKit has been split into two packages - @livekit/react-core and @livekit/react-components. This change allows developers to choose between a minimal set of helpers with no additional dependencies in react-core, or pre-built components with styled UI elements in react-components. The new structure aims to reduce bloat in the dependency tree and offer more flexibility for future updates. Developers can now download only the dependencies they need, while still having access to higher-level abstractions.