feat: Update release workflow and README

This commit introduces two main improvements:

1.  **Release Workflow:** The GitHub Actions workflow for creating
    releases has been updated to automatically generate a changelog
    based on commit history since the last tag. The release description
    is now managed via a HEREDOC, making it much easier for humans to
    edit. The workflow syntax has also been corrected for robustness.

2.  **README Banners:** The shield.io banner icons in the `README.md`
    are now linkable, pointing to their respective pages on GitHub
    (e.g., Releases, Issues, etc.).

Author: google-labs-jules[bot]