feat: add new toast demo components and enhance custom toast functionality

- Introduce new demo components: `AnchorClickDemo`, `AnchorSidesDemo`, `AnchorArrowDemo`, and `CustomNotificationDemo` to showcase various toast anchoring and styling options.
- Update `CustomDemo` to utilize a custom toast style for improved visual consistency.
- Enhance documentation with examples for click-anchored toasts and custom notifications, demonstrating new capabilities and styling options.

These additions improve the user experience by providing more flexible and visually appealing toast notifications.

Author: vcode-sh