✨ Support Bold and Italic Theme Tokens

[austincondiff]

Description

We should give theme tokens bold and italic support. Whenever these tokens appear in code, they will be bold and/or italic if the theme creator configured them to be so. We should add the ability to configure this in the theme details in settings.

Update: We were originally planning to allow themes to specify which tokens are bolded and italicized. We are now thinking that it makes more sense to abstract this away from the theme and provide a setting to manage this separately, providing good defaults that most likely won't be changed.