rc-menu: Core React Menu Component

rc-menu is a foundational, unstyled React UI component designed for building highly customizable and accessible hierarchical menus. It provides the core logic and composable primitives like `Menu`, `SubMenu`, and `MenuItem`, offering developers extensive control over styling and behavior. While widely adopted, the `rc-menu` package, currently at version `9.16.1`, is in a maintenance-only state with its last publish over a year ago. Active development and new features have migrated to the `@rc-component/menu` package (latest v1.2.0), which is the recommended choice for new projects and for existing users looking for ongoing support and enhancements. This component is often used as a base for more opinionated UI libraries, such as Ant Design's menu, due to its low-level control.