Issue with Mermaid Diagrams Not Rendering in GitHub App

[Usokkie]

Hello GitHub Team,

I am encountering an issue with Mermaid diagrams not rendering in the GitHub app. Instead of displaying the diagrams, the app shows only the raw Mermaid code. This issue can be reproduced by accessing the Mermaid repository through the GitHub app.

Steps to Reproduce:

Open the GitHub app. Navigate to the Mermaid repository. Attempt to view a Markdown document with embedded Mermaid diagrams.