Tracking issue: archiving this book

[BartMassey]

We are preparing to archive this book in favor of https://github.com/rust-embedded/discovery-mb2 . This book will still be available, but no new issues will be addressed etc. Tasks to achieve this:

• Fix the CI here to validate that the book is in a good state
• Investigate adding deprecation headers and/or footers to the book
• Triage issues and PRs that can be easily addressed
• Close remaining issues and PRs with a window to re-open
• Wait for a grace period (one month)?
• Archive this book

Comments and assistance welcome