Setting a custom font overwrites markdown styles

[peteralt]

Describe the bug
When I set a custom font for my .text TextStyle, it takes the new font, but any attributes like bold or italic are being overwritten and dismissed.

Sample:

Markdown(text)
    .markdownTextStyle(\.text) {
        FontFamily(.custom(CustomFont.pawp.fontName))
    }

Checklist

• I can reproduce this issue with a vanilla SwiftUI project.
• I can reproduce this issue using the main branch of this package.
• This bug hasn't been addressed in an existing GitHub issue.

Expected behavior
I would expect the styling to still apply even with the new custom font.

Version information

• MarkdownUI: 2.3.0
• OS: macOS 14.3.1 (23D60)
• Xcode: 15.3

Additional context
Add any other context about the problem here.