Release notes for v0.6.0 and documentation updates

[mdapena]

Initial Checks

• The code compiles successfully without any errors or warnings.
• I have personally tested these changes on my local environment.
• I have ensured that relevant documentation has been added or updated.
• I adhere to the project structure and code standards defined in the documentation.
• My code follows the established coding style guidelines.
• I have added tests for the new code (if applicable).
• All existing tests have passed successfully.

Description

This pull request includes various updates to the documentation, such as fixing broken links, updating contributing guidelines, and enhancing the 404 error page. Additionally, it tweaks the index and contributing sections and updates links in the README file to reflect the new release.