* Add doc-test to test website code snippets
Heavily inspired by tokio-rs/website repo.
* Fix code snippets to pass doc tests
Some code snippets are explicitly ignored and some are not run
to avoid having to include dependencies for one liners.
* Add website code snippet tests to CI
* Fix CI
* Remove doc-test from workspace
* Exclude doc-test from workspace
* Refactor code snippets and tests
Code snippets can import types from doc_test crate i.e.:
```rust
use doc_test::agents::EventBus;
```
This allows for moving some boilerplate away from the example and still
checks that the code compiles correctly.
Also some slight changes to some of the examples and the information
about `ComponentLink` which is deprecated.
* Move doc-test to packages
* Rename doc-test crate to website-test
The new name makes it more clear the purpose of this crate.
* fix ci
