Fixed: SyntaxError: '(' was never closed

FEAT: Added warning in preview for incorrect rendering of Code-Blocks

Changed the background of preview section tk be of the same dark color as of other elements.

Fixed preview rendering foreground color for better readability.

Added Support of Mermaid rendering.

Update Dockerfile

Update requirements.txt

Update requirements.txt

Update src/streamlit_app.py

Update requirements.txt

Update src/streamlit_app.py

initial commit

Duplicate from streamlit/streamlit-template-space