Mermaid support

Enclose the Mermaid code within three backticks and add the mermaid language qualifier, like so:

```mermaid
flowchart LR
    A["T101, Installation overview"] --> | prerequisite | B["T203, System requirements"]
    A --> | prerequisite | C["T305, Setup steps"]
```

flowchart LR
    A["T101, Installation overview"] --> | prerequisite | B["T203, System requirements"]
    A --> | prerequisite | C["T305, Setup steps"]

Another example

sankey-beta
Mahabharat,Potterworld,Value
Adityastra,Hot-air charm,1
Agneyastra,Incendio,1
Antardhan,Disillusionment charm,1
Bhargavastra,Incendio,1
Bhaskarastra,Lumos,1
Brahmashir,Avada kedavra,1
Brahmastra,Incendio,1
Jyotish,Lumos,1
Nag,Locomotor Mortis,1
Narayanastra,FiendFyre curse,1
Paash,Petrificus Totalus,1
Parjanyastra,Aguamenti,1
Pragnyastra,Rennervate,1
Pramohanastra,Stupefy,1
Sahasraghni,Sectumsempra,1
Salilastra,Aguamenti,1
Sammohan,Stupefy,1
Saurastra,Incendio,1
Shakti,Avada kedavra,1
Sudarshan chakra,Avada kedavra,1
Tvashtr,Polyjuice potion,1
Vaishnavastra,Avada kedavra,1
Vajra,Duro,1
Varunastra,Aguamenti,1
Vayavyastra,Deprimo,1
Vishoshan,Hot-air charm,1