docs(release-please): enhance README

[TartanLeGrand]

This pull request includes extensive updates to the release-please/README.md file to enhance the documentation for configuring and using the reusable release-please workflow. The changes provide clearer guidance on setting up configuration files, using the workflow in repositories, understanding different release types, and managing single projects versus monorepos.

Documentation enhancements:

• Updated the introduction to include a more descriptive explanation of the release-please workflow and added a link to the official GitHub page for further details.
• Added detailed sections on configuration files, including release-please-config.json and .release-please-manifest.json, with examples for both empty initialization and predefined versions.
• Provided a comprehensive guide on using the workflow in repositories, including a sample YAML file for triggering the workflow on a push to the main branch.
• Introduced a section on different release types supported by release-please, tailored for various ecosystems and languages, with a reference to the official documentation for more details.
• Explained use cases for single projects and monorepos, detailing how to configure and manage multiple packages within a monorepo setup.