Add support for fontawesome

[felickz]

Setup and configuration

• Mermaid version: 3.0.1
• MediaWiki version: 1.34.2
• PHP version: 7.3.22 (apache2handler )
• Database system (MySQL, PostgresQL, etc.) and version: MySql 5.7.32-log

Issue

graph TD
    A[Christmas] -->|Get money| B(Go shopping)
    B --> C{Let me think}
    C -->|One| D[Laptop]
    C -->|Two| E[iPhone]
    C -->|Three| F[fa:fa-bus Service Bus]

Recommendation:
Consider support or documentation how to configure fontawesome

• ex: mermaid-js.github.io
  

[kghbln]

Thanks for suggesting.