Gitlab Mermaid markdown does not support ER diagrams

Proposal

Entity Relationship diagrams are useful for describing data models, and have been supported by Mermaid for some time:

• Docs: https://mermaid.js.org/syntax/entityRelationshipDiagram.html
• Playground: https://mermaid.live/edit#pako:eNp10VFrwyAQB_CvIvfc9APkrUQZgXUZJi0UfHF6XYUkFqeFEfPdZ5aErR3zzeN3_5NzAGU1Qg7oqJHvTnaiJ-kUh7qp9oyTMW63cSCUPZdHxk_ZjlLO6prk5CI_HmyMWWYHUnGaLjm5tlLhP6Z8OVZlwZIS0Br51iI5Wydg1n-mPSQ7VGhua_aaNaH4g5S9oVvIXPsNsrJh-6RMr9qg16hXXtFD0WTFrmFPFT-tLUv9O7X30vT3_u59a7IA6zQ61GmGANhAh66TRqdlD1O3AH_BDgVMVONZhtZPCxgTlcHb-rNXkHsXcAPhqqXH5Yfm4vgFrhOHgA

Gitlab Mermaid Markdown should support Entity Relationship diagrams in addition to the Gantt, Sequence Diagram, and Flowchart diagrams which are currently supported: https://about.gitlab.com/handbook/tools-and-tips/mermaid/

This is an example Entity Relationship diagram definition:

erDiagram
    CUSTOMER }|..|{ DELIVERY-ADDRESS : has
    CUSTOMER ||--o{ ORDER : places
    CUSTOMER ||--o{ INVOICE : "liable for"
    DELIVERY-ADDRESS ||--o{ ORDER : receives
    INVOICE ||--|{ ORDER : covers
    ORDER ||--|{ ORDER-ITEM : includes
    PRODUCT-CATEGORY ||--|{ PRODUCT : contains
    PRODUCT ||--o{ ORDER-ITEM : "ordered in"

And this is what the rendered Entity Relationship diagram looks like: