System font variants such as monospaced don't work

[jcovin293]

In a RichText view with a Configuration with a fontType value of .monospaced or another value that is not .system, the website instead uses a serif font. Here is a code example:

RichText(html: "<h1>Hello World!</h1>", configuration: Configuration(
    fontType: .monospaced
))

This is similar to #49 where @RushanB describes the issue where custom fonts are not displaying as expected. This seems to be an issue with the CSS.