Mermaid rendering enable elk

Proposal

Right now it seems that the elk rendered is not enabled for mermaid. See this example:

---
config:
  layout: elk
  elk:
    mergeEdges: true
---
flowchart TB
    S --> QEu
    QEu -- No --> Ex --> E
    QEu -- Yes --> QS
    QS -- No --> QV
    QS -- Yes --> Ge --> E
    QV -- No --> Ge
    QV -- Yes --> Ex

---
config:
  layout: elk
  elk:
    mergeEdges: true
---
flowchart TB
    S --> QEu
    QEu -- No --> Ex --> E
    QEu -- Yes --> QS
    QS -- No --> QV
    QS -- Yes --> Ge --> E
    QV -- No --> Ge
    QV -- Yes --> Ex

Should render as follows:

However, at the time of writing this issue it renders as follows:

It seems that some issues are also experiencing this issue: https://forum.gitlab.com/t/enabling-mermaid-js-elk-rendered/93060. Also, on the Mermaid-JS GitHub there seem to be some issues about elk not being properly documented or enabled by default:

• https://github.com/mermaid-js/mermaid/issues/5782
• https://github.com/mermaid-js/mermaid/issues/6273