docs(material/theming): add tokens section to our docs

### Documentation Feedback

Add documentation to material.angular.io to list the tokens that our components expose.

#### Design

There are still some open questions that the team should discuss.

- Should we write a description for each token?
- Critiques:
- A unique description for every token may be too much data thrown at the user which the user might mentally filter out when looking through our docs.
- Many tokens are self-explanatory. It seems silly to write `"selected-checkmark-color": The color of the checkmark when the checkbox is selected`.
- A more useful approach may be to provide a subsection that explains terminology that is obscure to most users. For example, the section could describe the following:
- What `state-layer` commonly refers to.
- Listing the different states - `active`, `pressed`, etc. Material has [a page dedicated to this](https://m2.material.io/design/interaction/states.html#usage) we could also link to.
- Where should this token list live?
- IMO under the "API" tab for each component makes the most sense.

This design satisfies the following pain point for our users:

- CSS variables are difficult to identify / discover.

### Affected documentation page

https://material.angular.io/components/autocomplete/api

Commencez par la page de documentation de l’Autocomplete API concernée à l’adresse material.angular.io/components/autocomplete/api et examinez l’organisation de la documentation de l’API des composants. Résolvez avec l’équipe les questions en suspens concernant les descriptions des tokens, la terminologie et l’emplacement. La tâche est terminée lorsque les tokens CSS exposés peuvent être trouvés dans la documentation de l’API du composant approprié, avec des consignes de terminologie approuvées.

Rédigé par le modèle d'indexation à partir du texte de l'issue.