I've been thinking it'd be simpler to introduce `dyn Trait` via `&dyn
Trait` rather than waiting for the smart pointers section and `Box<dyn
Trait>`. This PR adds a slide to the Generics section that introduces
`&dyn Trait` and compares it to `&impl Trait`, juxtaposing
monomorphization and static dispatch against type-erasure and dynamic
dispatch. I've then updated the existing trait object slide to call back
to the earlier introduction, and call out that using `Box<dyn Trait>`
gives you an owned trait object rather than a borrowed one.
The files in this directory make up the content of the course. The files here
can include third-party content from ../third_party/ as well.
When we publish a translation of the course, we git restore the src/ and
third_party/ directories at the repository root back to the date listed in the
POT-Creation-Date header of the translation. It is crucial, that all
translatable content lives in those two directories. The other files (such as
book.toml and theme/) are not restored and we always use the latest version
of them.