Using Icons / Icon font (ex.font-awesome)

[corean]

http://bmcorser.github.io/fontawesome-markdown/

Alternatively, using user css ? I want this method in official Document.

[gynl]

I was making a mermaid chart and discoverd that this works :

```mermaid graph LR; A[fa:fa-gear] -->B(fa:fa-wrench); ```

I can understand that « Font awesome icons is not a common markdown feature », but it's a little bit ridiculous to be able to use it in graphs and not in texts.

It must be possible do something. 🙏

[abnerlee]

#2448

[amitbha]

need this feature