docs: Update README

[alessfg]

Proposed changes

This PR updates the README. In order to make the installation instructions easier, some file names used by the various GitHub Actions workflows have been renamed. As a small bonus, some other docs have had their **Note:** sections updated to use GitHub markdown alerts.

Checklist

Before creating a PR, run through this checklist and mark each as complete:

• [x] I have read the contributing guidelines.
• [x] I have signed the F5 Contributor License Agreement (CLA).
• [x] If applicable, I have added Molecule tests that prove my fix is effective or that my feature works.
• [x] If applicable, I have checked that any relevant Molecule tests pass after adding my changes.
• [x] I have updated any relevant documentation (defaults/main/*.yml, README.md and CHANGELOG.md).