feat(revealjs): Add Mermaid Plugin

[hgwood]

Hello and thanks! Could you give an example to show how it works?

[Adi3000]

Adding some slide like that

  ## Conception objet - Héritage

  <!-- .element: class="mermaid" style="text-align:center"-->
  ```mermaid
  classDiagram
      Vehicule <|--  Voiture
      Personne <|--  Scientifique
      Scientifique <|--  Ornithologue
      Animal <|--  Oiseau
      Animal <|--  Mamifère
      Mamifère <|--  Félin
      Mamifère <|--  Ruminant
      Félin <|--  Chat
      Félin <|--  Lion
      Oiseau <|-- Canard

Source : https://github.com/Zenika-Training/formation-java-debutant/blob/adrien/upgrade_20240911/Slides/java_04_conception_objet_et_uml.md