Support HTML in Markdown strings.

[RokeJulianLockhart]

Is your feature request related to a problem? Please describe.

https://mermaid.live/ is unable to render embedded HTML in Markdown strings, per https://mermaid.live/edit#pako:eNoVi0EOgjAQRa9C_pJwgsa44ga6c0wY2kGItDXDNMYQ7m55q7d4b4fPQeAwrfnrZ1Zr7j2lpmKy2YMwtKe0l1GvA-GJDlE08hLqtJ8lwWaJQnBVA-ubQOmoHRfLt1_ycKZFOpRPYJN-4ZdyhJt43eT4A6sNKwU.

Describe the solution you'd like

Render HTML in Markdown strings.

Describe alternatives you've considered

Per https://github.com/mermaid-js/mermaid/issues/5319#:~:text=1.%09Placeholder%0A%09%0A%09Placeholder-,additional%20context,-This%20cannot%20be, https://github.com/mermaid-js/mermaid/issues/5319#issue-2153013695 may be relevant, because remediating that reduces the immediate need for this functionality slightly.

Additional context

https://github.com/mjbvz/vscode-markdown-mermaid/issues/246#issue-2163953175

[github-actions[bot]]

This issue is stale because it has been open 90 days with no activity. Remove stale label or comment or this will be closed in 30 days

[RokeJulianLockhart]

https://github.com/mermaid-js/mermaid-live-editor/issues/1411#issuecomment-2151191350

@GitHub-Actions, don't.