3 bugs in markdown preview

[frenchcast1234]

There are 3 bugs in the Markdown preview:

• The font in code blocks is not monospaced.
• When the "Run" button is pressed while the keyboard is open, the keyboard remains open over the preview.
• The dot at the beginning of each list item appears black-on-black in dark mode.

[heckmon]

The markdown viewer is an external package used by the app. However I'll look into this.