Update rendered Markdown styles

[matt-west]

Fixes https://github.com/Automattic/dotcom-forge/issues/7670

Proposed Changes

• Cleaned up styles for rendered markdown.
• Added left/right margins to messages.
• Updated background for user messages.

Testing Instructions

• Open Studio using STUDIO_AI=true npm start
• Switch to the Assistant tab
• Enter a prompt to see example markdown styles:

Show me how all markdown elements would look when rendered

Pre-merge Checklist

• [ ] Have you checked for TypeScript, React or other console errors?

[matt-west]

@jeroenpf Interesting. Do you know if that's due to a limitation we've put in place?

[jeroenpf]

@jeroenpf Interesting. Do you know if that's due to a limitation we've put in place?

It seems that we've added that here: https://github.com/Automattic/studio/blob/trunk/src/index.ts#L197

@p-jackson might know more about this.

[matt-west]

Thanks! I’ve created an issue for fixing the images. https://github.com/Automattic/dotcom-forge/issues/7721