feat(skeleton): added Skeleton Loading with Examples

[dhavalveera]

This Pull Request introduces Skeleton Loading components to Flowbite-React, leveraging the Flowbite package. Skeleton Loading provides users with a seamless loading experience by displaying placeholders while content is being fetched or loaded. This enhancement includes various Skeleton components such as Skeleton, Skeleton Video, Skeleton Image, Skeleton Card, Skeleton List, and Skeleton Testimonial, ensuring a consistent loading UI across different types of content. With these additions, users will enjoy smoother transitions and improved usability, enhancing the overall user experience of Flowbite-React applications.

Pardon me for the variable names, please suggest a better naming convention.