Improve Documentation on Code-Splitting Behavior

[nonameebyrator985]

Issue Description

The README provides a brief overview of code-splitting and dynamic imports using Rollup, but it lacks detailed explanations regarding how the code-splitting functionality works and the implications for developers. It would be beneficial to expand the documentation to include:

1. Detailed Explanation of Code Splitting: Elaborate on how Rollup determines what code to split and the criteria it uses. Include information on chunking strategies and how to customize them.

2. Best Practices: Provide best practices for structuring applications to take full advantage of code-splitting. This could include directory structure examples, naming conventions for modules, or suggestions for managing dependencies.

3. Common Pitfalls: Discuss common issues or misunderstandings developers might face when implementing code-splitting and how to troubleshoot them.

4. Real-World Examples: Include examples of different use cases where code-splitting can be particularly beneficial, possibly demonstrating performance improvements.

By enhancing the README with this information, new users will have a better understanding of how to effectively use the code-splitting features of Rollup in their projects.