Move newtype pattern section for `Component` to the Book

## Issue

The following PR:

- bevyengine/bevy#4767,

introduces a paragraph in the API docs for `Component` about using the newtype pattern to implement the trait for foreign types. However, both @alice-i-cecile and myself, believe that this type of information is more suitable to the Bevy book.

## Solution

The following steps should be completed in order.

- [ ] Add paragraph and example to the Bevy book.
- [ ] Publish the version of the Bevy book containing the aforementioned change.
- [ ] Replace the paragraph and example in the API docs with a short sentence with a link to the right section of the Bevy book.

Start by locating the Component API documentation and the relevant Bevy book section, then review the existing newtype-pattern paragraph and example introduced by bevyengine/bevy#4767. Add equivalent book content, publish that book version, and replace the API-doc paragraph with a short link to the book section.

Written by the indexing model from the issue text.