Improve readme

[Xorcist137]

This pull request improves the README file with the following changes:

• Add a table of contents for easier navigation
• Provide more detailed installation and usage instructions
• Include comprehensive API documentation
• Add a section on customization options with examples
• Include information on browser compatibility
• Add a section on contributing to the project
• Include a changelog to track version updates

These improvements aim to make the documentation more user-friendly and informative for both new and existing users of PleaseWait.js.