Meta: about the book itself

Linking policy

We try to avoid links that easily become fragile.

Do:

• Link to docs.rs types to document the public API, but modify the link to use latest as the version.
• Link to modules in the source code.
• Create "named anchors" and embed source code directly.

Don't:

• Link to direct lines on github, even within a specific commit, unless you are trying to reference a historical piece of code ("how things were at the time").