fix(brand): Apply monospace-inline and monospace-block font family

[gadenbuie]

Fixes #1761

I mapped the typography.monospace-inline.family and typography.monospace-block.family values to Sass variables (font-family-monospace-inline and font-family-monospace-block, using the same naming as Quarto), but forgot to apply these in CSS rules.

While here, I updated the monospace inline rules to better catch "inline" code, i.e. code:not(pre > code) instead of just code.

The example in #1761 works with this change, as well as using different values for inline and block, e.g.

typography:
  monospace-inline:
    family: Arial